It was a pain to find the list on their site, so here are the languages supported by the editor:

APL, Asterisk, C, C++, Cobol, Java, C#, Scala, Clojure, CoffeeScript, Common Lisp, CSS, D, diff, ECL, Erlang, Gas, GitHub Flavored Markdown, GO, Groovy, Haskell, Haxe, ASP.NET, Embedded Javascript, JavaServer Pages, HTML, HTTP, Jade, JavaScript, JSON, TypeScript, Jinja2, LESS, LiveScript, Lua, Markdown (GitHub-flavour), mIRC, Nginx, NTriples, OCaml, Pascal, Perl, PHP, PHP(HTML), Pig, Plain Text, Properties files, Python, Cython, R, reStructuredText, Ruby, Rust, Sass, Scheme, SCSS, Shell, Sieve, Smalltalk, Smarty, SmartyMixed, SPARQL, SQL, MariaDB, sTeX, LaTeX, Tcl, TiddlyWiki, Tiki wiki, VB.NET, VBScript, Velocity, Verilog, XML, XQuery, YAML, Z80