[markdown mode] Fix handling of escaped characters

Issue #2792
[markdown mode] Make test pass
Set a min height on the lines element to prevent collapsing of wrapper

Issue #2765
Only apply IE<11 zooming compensation for client rects when getting rect from a range

It does not happen when measuring a node

Issue #2665
[closetag addon] Work better with htmlmixed mode

It now closes script and style tags when the slash is typed

Closes #2797
[javascript mode] Fix parsing of argument-less fat arrow functions

Closes #2794
[smalltalk mode] Use \s instead of space in regexps that denote whitespace

Closes #2796
Add a requireJS demo
Improve isWordChar() for Arabic language