most of the stuff in Basics/Fibrations is subsumed by Types/Sigma
move NullHomotopy into its own file
Merge pull request #581 from mikeshulman/fibrations

most of the stuff in Basics/Fibrations is subsumed by Types/Sigma
Merge pull request #582 from mikeshulman/nullhomotopy

move NullHomotopy into its own file
./autogen.sh