Syntax definition update

Adds syntax highlighting for crate paths, methods and macro invocations.
Adds placeholder names to some of snippets.
Improved highlighting of attribute definitions.

The color scheme for the screenshot can be downloaded from [here](https://dl.dropboxusercontent.com/u/675947/Neon.tmTheme).
![screen shot 2014-03-20 at 1 32 33 pm march 20](https://f.cloud.github.com/assets/1251233/2477271/d627fdaa-b06e-11e3-850b-4a2f420c311d.png)