Adds New Plugins

This fork:
- Adds two new plugins: CtrlP and Airline
- Sets default color scheme to "Solarized Dark"
- Edits README to provide instructions on how to fetch the latest commits of the plugins' repositories.

Side note:
CtrlP is mapped to <c-f> instead of <c-p>

I am new to Vim and Git, so please let me know if I am doing anything wrong, or if there is a better way to do things. I want to learn.

Thanks!