Merge pull request #49 from Hall/bug/notification_bad_access_crash

Fix bad access crash from NSNotificationCenter
Bumped version to 0.5.1
Declare iOS version in Podfile
Depend on AFNetworking
`pod install`
Cleared CocoaPod warning to inherit build setting OTHER_LDFLAGS
Added boilerplate category files to project
Added a helper to copy instance methods

We don't want to really copy the full implementation.
Strongly tied to AFNetworking/UIKit

This interface is exactly the same as for the UIKit helpers of AFNetworking. The implementation will be dynamically linked on runtime, and depends on private symbols. So we need to fix the version of AFNetworking/UIKit at least, we are depending on.
Added a subspec for MethodCopier
Added MRProgressView as intermediate class
Added "private" subspec for base class and let components depend on those
Use the new intermediate class
Made _progress ivar available for subclasses
Removed boilerplates for MRProgressView decendants
Added implementation
Added MRAFNetworkingSupportViewController
Integrated Pods in Example project
Removed manual static library reference from Example project
Implemented AFNetworking support example