Revert "PROTON-755: Update Ruby smoke tests to use Minitest"

This reverts commit 1d3a13863117cfca5aef56244b20773760428796.
Revert "PROTON-630: add setup.py for python bindings"

This reverts commit 4252758bd3772470bd255d034d3abea157429504.
restructured cmake file to support multiple sources
changed proton.py from a module into a package
NO-JIRA: More Ruby rdoc cleanup.

Turn off including the licensing headers repeatedly in the documentation
generated.
PROTON-752: Provide a non-blocking means to receive messages in Ruby.

To avoid changing the APIs or their intentions, a new class method is
added:

  Qpid::Proton::Receiver::receive_and_call

The method takes as arguments either an existing instance of Messenger
or else the parameters to create an instance, and also a code block to
be called with each message received.

The messenger is then put into passive mode and a new thread started. It
then monitors the messenger and, when a new message is received, passes
it to the block for processing.

To exit the messenger, the code would call Messenger#interrupt. The
thread then exits and the messenger stops processing.
Revert "PROTON-752: Provide a non-blocking means to receive messages in Ruby."

This reverts commit 0820a3722b6ab5c2a5a4dbfac3428de7d22c1c6e.

Reverting this change so we can have a review first.