Add versioning notes:  many of the signatures changed to allow the time used to be omitted (meaning use the current time) as of Python 2.1. Users who need cross-version portability need to know things like this.
Add versioning notes:  many of the signatures changed to allow the time
used to be omitted (meaning use the current time) as of Python 2.1.
Users who need cross-version portability need to know things like this.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator