Rotation fixes

Thanks for your AdBaseViewController. I've been playing around with it.

After finding the instruction to add -ObjC to the Other Linker Flags of your application target's build setting, everything began to work. I think you should add that to the set-up instructions. It's easy to miss if you don't read Google's AdMob instructions as well.

I was testing out rotation and it was working fine with iAds but not with gAds. So I decided to try to fix it and my changes are in the commits.

I've added changes to willAnimateRotationToInterfaceOrientation to fix positioning of GADs when rotation occurs and to make the main view resize correctly too as it does for iAds.

It seems to work on iPad & iPhone 5.1 + 6.0 when autoLayout is off on the storyboard.

Hope the changes are helpful. This is my first open source pull request. I hope I've done it ok!