[refs #182] Use new headings mixin courtesy of @thierrylemoulec

Still commented in LESS
Merge branch 'incoming' into v5.0.1

Escape unicode characters
renamed icon modifiers
corrected comment in sprite file for new classnames
v5.0.1 updates
Fix problem with main.less compiling

Close #5 - main.less used to failed when compiled when @base-font-family was set to something different than a pure string, due to the formatting operation