Changed UIImage to fix backbutton distortion

![screen shot 2014-05-27 at 7 32 07 pm](https://cloud.githubusercontent.com/assets/6572139/3149680/882c9d20-ea6d-11e3-8f36-5d2d167aa10f.png)
![screen shot 2014-05-27 at 7 17 07 pm](https://cloud.githubusercontent.com/assets/6572139/3149683/8b597ce8-ea6d-11e3-9a8a-281887d351de.png)

I saw this bug in the example project, when you rotate the screen the button becomes distorted. It appears to be a view did load issue, where the view is not being refreshed upon rotation. I've tried experimenting with didRotateFromInterfaceOrientation:(UIInterfaceOrientation)fromInterfaceOrientation method in tableviewcontroller, but it still does not refresh the view.

So in the mean time I removed the if statement in UIImage's backButtonImageWithColor method and set the button to be uniformly the same size regardless what orientation it is in. This is just meant to be a temporarily fix to relieve the distortion issue until a more permanent solution can be created.