Drop iOS 5.0 support, and support arm64

Adding this issue for discussion.

We still support iOS 5.0 in the Deployment Target.
iOS 6.0 and greater support enables arm64 support (64-bit) but not sure of any advantages there, really.

Also, this is consistent with our previous support where we only support the current iOS version and one version back. Also, finding a device with iOS 5 support (besides the iPad 1, which cannot have iOS 6 support) is becoming problematic.

iOS 6 API diffs from 5:
https://developer.apple.com/library/ios/releasenotes/General/iOS60APIDiffs/index.html

Apple's note regarding 64-bit support: https://developer.apple.com/news/index.php?id=9162013a

If you wish to continue to support iOS 6 then you will need to build for 32-bit only. Next month we will be making changes that will allow you to create a single app binary that supports 32-bit on iOS 6, as well as 32-bit and 64-bit on iOS 7.

So, based on that I think if we go ahead and support arm64 we wait for this 64-bit iOS fat binary functionality coming "next month". This probably will coincide with their Mavericks 10.9 OS and SDK release with the new accompanying Xcode bump.