[scss] Fix indentation issues

Closes #1776
[css mode] Fix unused variable
[coffeescript mode] Stop highlighting .keyword (.on/.off/.in) as error

Closes #1779
[matchtags addon] option added to highlight both tags
[matchtags addon] cleanup b3a1ed4

Issue #1781
[real-world uses] Add Tilemill
[real-world uses] Add uiCod
[show-hint addon] Fix broken inside-window-positioning code

Closes #1784
CSS lint addon with https://github.com/stubbornella/csslint
[css-lint addon] Don't add new deprecated code, fix trailing space

Issue #1782
Vim: raise mode change events

Signed-off-by: Chris Granger <ibdknox@gmail.com>
Update markselection.html

Demo was incorrectly named as showing 'Highlighter', fixed to 'Selection'
Get rid of top links in CONTRIBUTING.md

Issue #1786