Add OpenStack Swift as a git submodule

This allows developers to easily insert the python
debugger to the OpenStack Swift code which in turn
calls gluster-swift.

Using 'git submodule' allows developers to not only create
a clone of the OpenStack Swift repo locally, but
also automatically set the repo to the appropriate tested version.
This change also allows us to always match the version
of OpenStack Swift that gluster-swift has been tested against.

For this change, the submodule of OpenStack Swift has
been set to version 1.9.1 which, according to the RDO
rpms, it is commit id 95bcd7180c546f91414c2493d343fe1a4ae3ce44.

Here is how developers can setup their repo after this change:

$ git submodule init
$ git submodule update

Now that the correct version of the OpenStack Swift
code has been cloned to the modules directory, it can be
used for debugging during development.  First we need
to setup a link called 'swift' to point to the python
code from the root of the gluster-swift repo as follows:

$ ln -s swift modules/swift/swift

Here is simple example of how to debug an object PUT command.
First, we need to add the following line:
`import pdb ; pdb.set_trace`
to swift/proxy/controllers/obj.py at line 818.

To execute the debug line added above, we can use the following
unit test:

$ nosetests -v -s -exe test/unit/proxy/test_server.py

Change-Id: I01dd58954e5ef139208a1132140c6c83ada82c18
Signed-off-by: Luis Pabon <lpabon@redhat.com>
Reviewed-on: http://review.gluster.org/5787
Reviewed-by: Chetan Risbud <crisbud@redhat.com>
Tested-by: Chetan Risbud <crisbud@redhat.com>
Reviewed-by: Peter Portante <pportant@redhat.com>