Spec for parse_emails
Added a spec for get_emails_for
Added spec for #get_circles
Moved the default glassfrog uri into EmailGrabber.

It went into the printer because the ARGV did, not for a good reason.
Bump ruby to 2.0.0
Raise an exception if the requested circle is unknown.
Refactor to make #get_emails_for shorter
Refactor to get rid of silly CONSTANT
Moved error handling for nonexistent circles