Use NSURL methods instead of CFURL functions

* Replace CFURLCopyUserName with -[NSURL user]
* Replace CFURLCopyPassword with -[NSURL password]
Rename the `username` variable to `user`
Merge pull request #743 from 0xced/NSURL-user-password

Use NSURL methods instead of CFURL functions
Fix race condition in UIImageView+AFNetworking
[Issue #751] Removing NSURLConnectionDataDelegate from AFURLConnectionOperation's declared protocols
Suppressing warning caused by AFHTTPBodyPart -hasBytesAvailable not having default condition in switch statement
Merge branch 'master' of github.com:AFNetworking/AFNetworking
Merge pull request #747 from peymano/race-condition-fix-in-uiimageview

Fix race condition in UIImageView+AFNetworking
Enqueuing operation in upload example rather than calling -start directly
Whitespace formatting
Using early return in AFURLConnectionOperation -setState: to avoid posting notifications in lock
[Issue #737] Updating default Accept-Language header value in AFHTTPClient
Whitespace formatting by Xcode re-indentation
Merge branch 'experimental-issue-738'

Conflicts:
	AFNetworking/AFURLConnectionOperation.m
Fixing @param name to correspond to actual parameter (filename -> fileName)
Fixing warning caused by default statement in switch statement that covered all enumeration values
Revert "Fixing warning caused by default statement in switch statement that covered all enumeration values"

This reverts commit b5c48f13a1d42952da78ab3027b7d804048f525b.
Fix  [Issue #751]
Serialize calls to responseJSON using a lock.

AFJSONRequestOperation's completion path calls `responseJSON` from a
processing queue.  Because `responseJSON` "lazily" deserializes the
response data into a JSON object, it needs to be protected against
concurrent access from other queues (threads).

For example, `AFNetworkingOperationDidFinishNotification` is posted
when the operation finishes but perhaps before that processing queue
has finishing executing.  Notification observers who also access
`responseJSON` end up in a race with that queue that often leads to a
crash.

We reuse the existing lock from our AFURLConnectionOperation base
class.
[Issue #769] Resolving asymmetry in cached image case for UIImageView category