Change underlying type of KeepValue
Implement inheritance of priorities
Define default priority
Remove priority inheritance, always use Required
Update code to not use deprecated APIs
Provide function to set default priorities
Update -keepAt:/min:/max: methods to use new APIs
Add macros to build KeepValues easily
Merge branch 'complex'

* complex:
  Add macros to build KeepValues easily
  Update -keepAt:/min:/max: methods to use new APIs
  Provide function to set default priorities
  Update code to not use deprecated APIs
  Remove priority inheritance, always use Required
  Define default priority
  Implement inheritance of priorities
  Change underlying type of KeepValue
Update podspec