Compile AFNetworking for iOS 6 and iOS 7

- By using __IPHONE_OS_VERSION_MAX_ALLOWED and
  __MAC_OS_X_VERSION_MAX_ALLOWED, it will allow users who have minimum
  of iOS 6 or Mac OSX 10.8 to levarage NSURLSession for users on iOS 7
  and Mac OSX 10.9
Compile AFNetworking for iOS 6 and iOS 7

- By using __IPHONE_OS_VERSION_MAX_ALLOWED and
  __MAC_OS_X_VERSION_MAX_ALLOWED, it will allow users who have minimum
  of iOS 6 or Mac OSX 10.8 to levarage NSURLSession for users on iOS 7
  and Mac OSX 10.9
Remove the lock podfile

It doesn't matter what version pods are for testing, this isn't a production
app. It's more cumbersome to ensure the lockfile is in-sync than the benefits
it's worth.
Add image response serializer to UIButton+AFNetworking.
Without this fix, the responseObject is nil and the image does not get updated.
Fixes #1453. Completion block for group of requests should be called after all completion blocks have finished executing.
Merge pull request #1462 from kylef/tests

Fix the unit tests
Merge pull request #1461 from DenHeadless/master

Fix completion blocks call order when executing batch of requests
Minor reformatting
Merge pull request #1448 from samgro/master

Add image response serializer to UIButton+AFNetworking. Fixes #1447.
[Issue #1448] Adding missing image serializer for background request operation
Minor formatting
[Issue #1464] Fixing setPinnedCertificates: and pinned public keys
[Issue #1423] Fixing compound serializer error handling
[Issue #1422] Adding locks around access to mutiple delegates dictionary for AFURLSessionManager
[Issue #1418] Initializing URL session delegate upload and download progress
[Issue #1418] Fixing documentation of NSProgress parameters
[Issue #1455] Wrapping OSStatus and NSCAssert with NS_BLOCK_ASSERTIONS macro to prevent unused variable
Fix the mac example

- Set the deploy target to 10.9 since it depends on 10.9
- Vendor all the new required files from AFNetworking

Fixes #1459
Merge pull request #1466 from kylef/examples

Fix the mac example
Fix README typo