Add new theme: Iterate

Features
* Hide information when not relevant
* Responsively wrap to prompt to new line if information is over half the console width
* Padding on right not left
* Only show RVM information if not using default ruby
* Include git ahead/behind/stash information


80x24
![image](https://cloud.githubusercontent.com/assets/1319655/2923152/3a763194-d70e-11e3-9e52-3740de9bbb9b.png)


132x24
![image](https://cloud.githubusercontent.com/assets/1319655/2923143/14b8e0d2-d70e-11e3-9706-f5341fff8e5c.png)