When I trying build CKCountdownButton as a framework in Xcode 6.3, it complains with
warning: no umbrella header found for target 'CKCountdownButton', module map will not be generated
Then when I import this framework in other project, it failed with No such module 'CKCountdownButton'
CKCountdownButton.h in framework fixed this issue.
I think the umbrella header means the header file with same name like Framework