Merged 416109-arbitrary-endpoints [r=therve,jkakar] [f=416109].
The primary change of this branch is support of arbitrary endpoints (needed for
the support of Eucalyptus). In addition, the following was also performed:
* Added a parse utility function from Twisted
* Created a testing subpackage for use by txAWS unit tests
* Created a service module for abstracting regions and associated
serices/credentials