complete slides for decorators and context managers
add code samples for context managers.
Merge branch 'master' of github.com:cewing/codefellows_f2_python
add homework for context managers
a little clean up of the iterator/generator slides.
Merge branch 'master' of https://github.com/cewing/codefellows_f2_python
Merge branch 'master' of github.com:codefellows/sea-c15-python