Add mailman gem
Set Mail.delivery_method to :test in the test env.
Add entry point for new email in Messages::Email.receive
Add bin/mailman script to fetch email via IMAP
Update README.md with mailman info
Add Sequential gem to handle conversation number
Merge branch 'wip-50-email-fetch-rebased' of https://github.com/austinylin/supportly-web into austinylin-wip-50-email-fetch-rebased

Conflicts:
	Procfile