And add marker changes to the undo history, so that
un/redoing doesn't cause 'ghost' markers to appear.

Closes #882

And ensure we don't set cursor height to something negative.

Closes #864

- Add options to Markdown mode to make it easier to extend
- Add GFM text overlay
  - SHA, User@SHA, and User/Project@SHA
  - #Num, User/#Num, and User/Project#Num
  - Vanilla URLs
- Add GFM-specific tests
- Fix overlay code so blankLine() is called
- Fix GFM for v3

I don't know what they were thinking, but this, on
recent Opera versions, seems to give the correct
result.

Closes #10

They were completely broken due to really fragile use of html
selectors. Should work much better now in test framework.

Closes #796

Huge refactor of lib/codemirror.js. Most code is now top-level (in the
module wrapper function) rather than inside of the CodeMirror
constructor sharing a huge amount of state.

A CodeMirror instance now has (non-public) `display`, `view`, and
`options` properties that describe its state. The display holds the
editor's DOM structure and associated state, view represents a view on
a document, containing `doc`, `sel`, `overwrite`, `scrollTop`, and
`scrollLeft` properties. The `doc` itself contains its history.

(It is not yet possible to switch views and documents in and out of an
editor, but this does start clearing the way towards that.)

Cleans up the implementation of marked ranges, makes the data
structure for markers-within-a-line persistant, and attaches them to
the lines stored in the undo history when necessary.

Closes #675

- Added link to tests on mode page
- More consistent naming with CSS spec (some of the previous var naming was completely incorrect/misleading)
- Improved highlighting
  - Match vendor prefixes
  - Check for known properties and values (known properties are bold, unknown are not)
  - Added highlighting for media queries
- Cleaner stacking of state

Add a text-shadow behind test progress text so it's readable while the progress bar hasn't passed yet.

If two tests have the name "foo", the second should appear as "foo_2", but instead it appeared as "foo_3".

- Move unchanging styles for #progress to style sheet

- Forgot to update testCM() when I added the `verbose` option

We do still support IE7/8.

Also removes some non-CodeMirror-code-style things like left-aligned
commas and semicolons.

There are now enough tests to make this take a serious amount of time.

A 0 timeout seems to work just as well.

- Integrated stex and Markdown mode tests into main test harness

- Added ability to restart tests partway through

- Added verbose option, to add message to output for *every* test

- Added ability to show verbose messages and run specific tests or all tests for 1+ mode(s) via location.hash

- Added support for custom messages (either return value [pass] or throw value [fail])

- Switched away from .innerHTML, .write(), etc in most places

- Make the progress bar actually 0px wide when 0% complete (and still keep padding)

- Added link to tests from each mode's demo page

Markdown mode

- Add additional link tests and correctly match link titles on next
  line.

- Adjust tests code so sections (including "Basics") can be rearranged
  and removed easily without breaking the script.

- Add tests and fix highlighting for lists.

Test harness

- Sort styles in mode test script so "quote string" = "string quote".

(Squashed commit. Below are the original commit messages:)

- Add highlighting test for Markdown for consecutive backticks.

- Make it possible to wrap inline code in multiple backticks.

- Add highlighting test for Markdown mode to only allow a single space
  to separate brackets.

- Make it possible to separate bracket groups with a space.

- Allow for horizontal rules to use dashes.

- Allow for *any* number of -'s or ='s for setex headers.

- Remove requirement that the text for setext headers have to be
  highlighted.

- Might revisit someday to work on this, but in the meantime, it's
  better to prevent regressions than to be picky about what would be
  highlighted in an ideal world.

- Correctly match single line footnotes with title.

- Match inline links in Markdown mode.

- Don't match unclosed code blocks.

- Get mode test highlighter in line with CodeMirror.highlight().

- It would be nice to use all native functions, to avoid having to update this manually each time.

- Fix tests per fixes made to mode test highlighter.

- Properly handle multiple classes for mode tests.

- More correct handling of EM and STRONG in Markdown mode.

  Per Markdown documentation: "You can use whichever style you prefer;
  the lone restriction is that the same character must be used to open
  and close an emphasis span." # This is the 15th commit message:

- Allow escaping of * and _ by surrounding with spaces.

  Per Markdown documentation:

  "But if you surround an * or _ with spaces, it’ll be treated as a
  literal asterisk or underscore."

- More correct support for inline code blocks.

- Adjust Markdown highlighting tests to fit readability, rather than
  100% conformance with Markdown documentation.

  Although unclosed italics, bold, and inline code would not be
  formatted by a Markdown parser, it is extremely helpful to have the
  styles added even when it is not yet closed. It may be a good idea
  to add an 'incomplete' flag for each at some point, in order to
  style it (and mark it) as different. Perhaps piggyback off of
  "error".

The off pun is rather awful, but it does have precedent, and is
more succinct.

Fixes a problem where the editor would always be 30 pixels smaller
than its set height.

The height is now set on the outer wrapper DIV again, and some
height: 100% tricks are used to make height information flow
both ways (inside-out in demo/resize.html mode, outside-in in
normal, fixed-height mode).

Closes #775

Fix bad rules in themes, measure width correctly.

It is now more structured (knows about ranges) and allows automatic
unfolding when the cursor enters the folded range.

This will make fixedGutter work properly, and make it the only model
(no more gutter that scrolls out of view).

Also reorganizes the basic css file to be easier to modify for users.

Issue #730

Issue #294

No more random {x,y,yBot} thrown into the mix.

Experimental for now.

- Multiple gutters are explicitly created with the gutters
  option
- Markers go into a specific gutter, new setGutterMarker,
  clearGutter methods
- The line number gutter is separate
- The 'fixedGutter' feature is removed (painful to do now,
  was shaky anyway)