updated readme
Merge pull request #46 from jwadkins/readme_update

updated readme
Removed two returns that could never get called
Added EC2System as a new mgmt_system

- No docs yet
- Not used in tests yet
- Added boto to requirements
I hope you like docstrings.
Stripped trailing whtiespace
More minor PEP8ness
Added EC2System to setup_mgmt_system fixture