Patch — Allow pre-formatted messages to be enqueued.

[fs]

In certain situations I want to send preexisting messages which only exist in a string. The enqueue should handle these messages as well. Attached a patch (with test case) which resolves this ticket.

Proposed usage:

turbomail.enqueue(dict(sender="foo@bar.example", 
                       recipients=["sales@bar.example"], 
                       message=msg_string))

[amcgregor]

Patch applied as of r27.