Added AMQPMessage for test purposes.
Added from __init__ import..

This is important, because otherwise importing from submodules fails.
Added test for MARCXMLRecord class.
Added some documentation, code cleaned a lot.
Added lot of docstrings.

Refactoring aplied to classnames better reflect nature of communication
with aleph.
Docstrings/documentation updated.
amqp.py removed - communication won't be handled in this module.

Everything that is needed for module to be able to communicate thru AMQP
is in __init__.py.