Update getLongTitle to be project relative

TabView uses getLongTitle to provide a less ambiguous file title should multiple files have the same name.  However if these files also happen to be in a sub folder of the same name the ambiguity remains.

By increasing the long title to be relative from the project root this ambiguity is removed.

Before:
![screen shot 2014-05-22 at 21 33 36](https://cloud.githubusercontent.com/assets/196630/3060049/902dcd96-e1f3-11e3-91d0-d98b71bed480.png)

After:
![screen shot 2014-05-22 at 21 38 46](https://cloud.githubusercontent.com/assets/196630/3060054/9d317b14-e1f3-11e3-9632-94b7253c32e1.png)

Applies to atom/tabs#57