Issue #892

Because laying out the whole thing again is more work than what is
saved by manipulating it in hidden state.

Issue #892

To save round-trips on layout.

Speeds up rendering by 33% on Chrome.

Issue #892

(git is the authoritative source of who wrote what)

Removes the kludge with the vertical scrollbar trying to handle
all wheel events.

Issue #810

Issue #811

It messes up parent relationships in inner nodes, and we'll re-use
the marker and widget nodes later.

Closes #890

The reason for putting them in doc turned out to be misguided

Simply use top-level functions + a plain object.

Detect when new position falls outside of a line, and retry. Also
replaces the kludgy widget compensation code.

Closes #886

Multi-line Lua comments start with "--[[", not "--["

Issue #881

By growing the vertical scrollbar to cover the whole editor when a wheel scroll
is taking place.

(This to avoid manually handling wheel events, for which there doesn't appear
to be any way that feels native across browsers.)

Closes #810

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

Closes #882

So that, even though they share a z-index, they overlay the text and
marked spans.

Closes #883

This basically matches the CSS3 spec (except it doesn't match non-ascii characters).

Closes #875

Closes #857

Add alignWithWord option to be able to turn that off.

Some sites set them to auto, which messes up our cursor (and probably more)

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

Closes #864

There are cases when widget could be a different repsentation of code, so while folding the code 
one may want to show widgets for hidden lines.

I added showWidgets parameter to foldLines, if set it allows widgets for hidden lines to be shown.
Here is a simple showcase where this functionality is needed:
http://uxcandy.com/~boomyjee/dayside/plugins/teapot-copy/