Fixed memory leak with NSURLSession

It looks like holding the reference for the NSURLSession until you no longer need it may solve the leak if in dealloc we make sure to cancel and invalidate using [<code>[self.urlSession invalidateAndCancel]</code>](https://developer.apple.com/library/ios/documentation/Foundation/Reference/NSURLSession_class/Introduction/Introduction.html#//apple_ref/occ/instm/NSURLSession/invalidateAndCancel)

A better solution would be to have only one session object per application lifetime and manager it on another class responsible for handling requests.

I also fixed some stuff I noticed regarding a known bug in iOS7 with the Separator of <code>UITableViewCells</code> and added a  <code>gitignore</code> file.