Fix typo
Merge pull request #1869 from mickeyreiss/patch-1

Fix typo
Change valueForKey to valueForKeyPath to fix crash on retrieving params names
Fix incorrect method name.

The method for uploading images as a multipart form was outdated.
Refactor to allow each sub spec to compile on its own
Standardize on RKCoreData.h for __has_include() test
Bump version to v0.23.1
Merge branch 'release/0.23.1' into development