[Objective-C] Remove CocoaPods ignores

We shouldn't be ignoring these, it's down to the user and we shouldn't enforce them to ignore the `Pods/` directory

http://guides.cocoapods.org/using/using-cocoapods.html#should-i-ignore-the-pods-directory-in-source-control?
[Objective-C] Add a note about CocoaPod's Pods/
Merge pull request #998 from kylef/patch-1

[Objective-C] Comment out CocoaPods rules