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

Get rid of eolSpanContent mess.

Preparation for RTL text handling.

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)

Closes #738

Closes #753

Closes #751

When dragging there is no src attribute needed on the dummy image.

Though it doesn't seem to have any observable effect on Chrome.

@peterkroon Where does the image actually show up?

It produces a bogus horizontal scrollbar there.

(codemirror2 -> codemirror)

Closes #736

Closes #737

Closes #738

Was "};" => "}\n;" before, "};" => "};\n" now.

Markdown mode: fixed issue with [bracket quoted words] that aren't actually links being tokenized as links

Now that the scroller div has its own vertical scrollbar, we no longer
need to explicitly update the scrollbar during updateDisplay.

https://groups.google.com/forum/?fromgroups#!topic/CodeMirror/PKCQHasHuhE%5B1-25%5D

This is a temporary kludge. I hope we'll be able to find a better
solution. (This should bring back the flicker issue on Lion.)

Issue #727