Add LESS language support

All auto-detect tests are passing.  Styles should largely inherit from CSS and other languages, although I can certainly add styles to default and other stylesheets if needed.  Here's a preview (using a custom stylesheet to show the detail in parsing):

![screen shot 2013-12-18 at 6 17 53 pm](https://f.cloud.github.com/assets/2146819/1779507/6f46f3d6-684b-11e3-9527-cf10b19bb7af.png)