Pycept cleanup

@subutai - please review

This does the following:

1. Uses API key from environment if you don't pass one to the constructor.
2. Updates the README to reflect change to new API.
3. Does some style cleanup to match Numenta style guide - Subutai please let me know if we decided to use a more canonical Python format instead of the Numenta style guide (I saw a lot of snake_case variables).