Updated the change log and pod spec for release 1.5.1.

Removed a duplicated step from the release instructions.

Updated the changelog for release 1.4.

Updated the change log.

Updated the change log.

Updated the change log.

Updated the change log.

Updated the base SDK in the QC plugin project.

Removed the SDK Build group from the iOS project.

Fixed an axis title positioning bug in CPAxisTitle. Fixed issue core-…

…plot#275.