[meta addon] Add Embedded Ruby (erb) as a htmlembedded mode

The mime type is currently accounted for in the htmlembedded definition, but erb
is not listed in the `mode/meta.js` index.
[real-world uses] Add JSER
[real-world uses] Added Waliki

a wiki engine
[markdown mode] Fix bad require call
[continuelist addon] Fix a bug in matching ordered list
[html-hint addon] Remove executable bit
[vim] add support for paragraph text object
Make default scroll style for CodeMirror-scroller 'scroll'

And manually compensate for our own scrollbar sizes.

This way, we're no longer dependent on the size of our scrollbars
being the same as the size of native scrollbars, and can start to
think about custom scrollbars.
Add some scroll model tests
Add the scrollbarStyle option

Implements a pluggable scrollbar model. Interface not documented yet,
but quite simple (see forthcoming simplescrollbars addon)
[simplescrollbars addon] Add
Expose CodeMirror.wheelEventPixels
Fix bug that allowed visibleLines to return an empty viewport
Implement annotated scrollbars, rig search addon to show them
[merge addon] Support aligning both panels by adding empty space
[merge addon] Allow collapsing of identical stretches of text

Using the collapseIdentical option.
[merge demo] Describe aligning and collapsing functionality
[merge addon] Properly document
Fix bug introduced by b6be5c272349ffdad0b9
Cypher mode: add EXPLAIN and PROFILE keywords.