Add LiveScript syntax

The file `LiveScript.sublime-syntax` is a pure export from a licenced version
of Sublime Text, Version 3.1.1, Build 3176 with
assets/syntaxes/02_Extra/LiveScript/Syntaxes/LiveScript.tmLanguage as the source
file.

CHANGELOG.md

@@ -30,6 +30,7 @@
 - Syslog highlighting improvements, see #1793 (@scop)
 - Added support for `slim` syntax, see #1693 (@mfinelli)
 - Racket, see #1884 (@jubnzv)
+- LiveScript, see #1915 (@Enselic)
 
 ## New themes