0.1: multiple updates (includding API changes)

- Added Email class extending from python message object
- Moved get_json_attachment function to new Email class
- Added 'gzipped' option to get_json_attachment (now can get a gzipped
JSON attachment file)
- Added JSON attachment options to send_email function
- Deprecated send_two_part_email function (will be removed)
- Corrected some typos