Praat syntax highlighting rules

Adds syntax highlighting for [Praat](http://www.praat.org), a GPL acoustic analysis software extensively used by phoneticians and others in related fields. Included is a syntax testing document which tests most cases using the recently updated new syntax and the old-style syhntax (now called "shorthand").

The syntax highlighting is the only thing included in this branch, but maybe in the future this can be extended.

it might be good to add indentation based folding here, similar to https://github.com/ajaxorg/ace/blob/master/lib/ace/mode/ruby.js#L39