Replaces occurrences of `AFHTTPSerializer`

Changes some comments where either AFHTTPRequestSerializer or
AFHTTPResponseSerializer should be user insted of AFHTTPSerializer
Finalizing #1412 by fixing __IPHONE_OS_VERSION_MIN_REQUIRED to __IPHONE_OS_VERSION_MAX_ALLOWED in `AFHTTPSessionManager` too ( #1412 only did it in `AFURLSessionManager` )
Merge pull request #1486 from AliSoftware/master

Finalizing #1412 fix for __IPHONE_OS_VERSION_MIN_REQUIRED
Merge pull request #1485 from brunokoga/master

Replaces occurrences of `AFHTTPSerializer`