Update README

JSON does not have option since https://github.com/Alamofire/Alamofire/commit/9f7c36531d6a23ab8b5bb3f456fb7a7c79370d65
Adding MARK labels
[Issue #91] Fixing optional HTTP method in Printable and DebugPrintable
Merge pull request #61 from MacKeeper/master

Update README
Replace default headers with session configuration HTTPAdditionalHeaders
[Issue #96] Fixing unit tests
Removing charset parameter from Content-Type headers
Linking and Copying framework in build phase to enable running on iOS device
Adding more comprehensive installation instructions
Update README.md
Update README.md