Update source/session02.rst

Replace print statements with print functions
Replace old repo name in examples
Improve whitespace on some examples with cramped whitespace
Merge branch 'master' into print_function
Update source/session01.rst

Replace old student repo in examples with sea-c28-students
Update source/session03.rst

Replace print statements with corresponding print functions
Resolve merge conflicts between cewing:master and jefrailey:print_function

Keep repo reference fix from cewing:master (19a359274152c3d9b5fa83681065b4a6f9b58a8b)
Merge pull request #2 from jefrailey/print_function

Print function - Session02
update session 3, particularly the mailroom madness assignment.
update session 4
fix borked link to python docs

Thanks to @Santhu13 for the reminder