Merge branch 'ackermann'

The series.py and ackermann.py work is done.
Merge remote-tracking branch 'upstream/master'

Incorporating any changes from upstream master to my local
repository.
First commit of list_lab. Done through 'Series 2'
list_lab.py should be done now.
Not sure if I've first-committed rot13.py yet. In any case, here it is...
Everything is getting a little intricate. Need to review code by printing/marking-up. Not at all done.
Added tests to rot13.py
rot13 and list_lab should be in final form
mailroom progress
Merge branch 'master' of https://github.com/codefellows/sea-c15-python

Pulling updates to local repo.
Will want to add some comments, but pretty much done...w
mailroom.py is done.
Minor PEP8 whitespace cleanup.
Merge pull request #66 from jay-tyler/mailroom

mailroom.py submission