v2.1.2 Release

Notable changes:

• #139 & #140 tvOS support in the podspec
• #141 & #143 -Wreserved-id-macro issues
• #145 add a default_subspecs for the podspec to avoid tests specific code defaulting to be in apps when developers to use specific subspecs.
• #146 & #147 Fixes for Xcode9 and newer SDKs.