Updated to API v1.6

You have done some great work on the API lib!
Guerrilla Mail recently added support for custom domains, so I've added this to the lib
https://docs.google.com/document/d/1Qw5KQP1j57BPTDmms5nspe-QAjNEsNg8cQHpAAycYNM/edit?hl=en#
Also, I've added SSL support, with the non SSL access getting phased out in the future.
Thanks.