Adds requirements

new file:   requirements.txt
Move requirement files :/

renamed:    sessions/requirements.txt -> requirements.txt
Adds more session functionality

modified:   pizza.py
Ignore os x files

modified:   .gitignore
Adds initial version of sessions module

later I sould use databases for this, but so far
we're good

new file:   sessions.py
Adds templates for listing active sessions and starting session

new file:   templates/active_sessions.jinja
new file:   templates/start_session.jinja