Update languages.js documentation

[iabw]

I wanted to suggest that the languages configuration be called out in the README a little more.

I also wanted to ask three questions which I don't think the documentation fully cover.

1. The names property of each language config isn't explained in the documentation at the top of languages.js. What is this used for?
2. Although literals is explained as "Quoted strings are ignored when looking for comment delimiters. Any extra literals go here", I don't really understand what that means or what it would be used for. The only examples are the regexes under JS and Coffeescript that don't illustrate why I might add additional literals. Would you be able to clarify that?
3. How do commentStart and commentEnd differ from comment and multiLine? They're not mentioned in the docs at the top of the file either.