Added 1.2 functions and better highlighting

- Comment syntax (`{{/* comment */}}`)
- Dot identifiers (`.`, `.Some.Dot.Path`) treated as separate from the enclosure (so they're not highlighted as `PreProc`)
- Variables given special treatment
- Functions made into `Function`s to set them apart from control flow statements
- Added Go 1.2 functions (`eq`, `ne`, `lt`, `gt`, etc.). Strictly backwards-compatible.