Added highlighting for functions

Without patch:
![vimerl func without patch](https://cloud.githubusercontent.com/assets/234891/2969856/aabbeef6-db52-11e3-85d8-6e332f933c3b.png)

With patch:
![vimerl func with patch](https://cloud.githubusercontent.com/assets/234891/2969858/b78b2fac-db52-11e3-8f44-286c9e2ba223.png)

Vim 7.4 & Ubuntu 13.10 with theme https://github.com/morhetz/gruvbox (dark)