WIP: Highlight

Hi,

Can you please review this work-in-process change? It's still not ready to merge. I still should write tests and also I have several questions:
* How to correctly send unsaved files to gocode? There can be several unsaved files; currently I'm passing one file to stdin, but
    * go parser doesn't see other files from package
    * this approach makes impossible to handle other unsaved files.
* Which highlighting output formats should be added to `qtjson`?