Changing NSError ** parameter to NSError * __autoreleasing *

Minor reformatting of AFHTTPClient method signatures
Add error when building without ARC to a central file.
Import UIKit to avoid build errors from UIDevice references in "User-Agent" default header. closes AFNetworking/AFNetworking#542
Merge pull request #543 from blakewatters/bugfix/import-uikit-in-client

Conditionally Import UIKit in AFHTTPClient to avoid build errors
Merge pull request #541 from tewha/master

Add error when building without ARC
Updating notes about ARC and requirements
[Issue #546][Issue #513] Adding AFMultipartFormData -throttleBandwidthWithPacketSize:delay:
Merge branch 'master' of github.com:AFNetworking/AFNetworking
Fixing warnings detected by -Weverything
Fixing compiler warnings relating to incorrect use of #if rather than #ifdef
Fixing warnings triggered by -Weverything flag

Adding __attribute__((noreturn)) to networkRequestThreadEntryPoint
Fixing warnings triggered by -Weverything flag

Explicitly covering all enum values in switch statements

Removing unused, unsynthesized properties

Adding missing synthesizers for properties

Fixing misuse of compiler macro
Fixing misuse of #if instead of #ifdef for AF_DISPATCH_RETAIN_RELEASE
-initWithBaseURL: will now raise an exception with a nil URL parameter. This enforces what the code comments say.

Without this, Reachability might cause the application to crash on iOS 6 if the baseURL is nil.
[Issue #548] Reverting breaking changes from b317c7d5d9e23f2516b6b917249eb4705cab74e4
Merge pull request #547 from jbrennan/bugfix/httpclient-nil-url-exception

-[AFHTTPClient initWithBaseURL:] will now raise an exception with a nil URL parameter.
[Issue #554] Re-adding AFMultipartFormData -appendPartWithHeaders:body:
[Issue #555] Leaving square brackets unescaped in query string parameters
Merge branch 'master' of github.com:AFNetworking/AFNetworking

Conflicts:
	AFNetworking/AFHTTPClient.m
Removing outdated note about 3rd party JSON libraries