Unit tests require running Cassandra

[Ilya Sviridov]

https://review.openstack.org/#/c/77299/

We have to group our tests and run only dependency free group as Jenkins check.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/77620

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/77620
Committed: https://git.openstack.org/cgit/stackforge/magnetodb/commit/?id=6f1ea4e2f96eda6113810f37c42e49177e18961f
Submitter: Jenkins
Branch: master

commit 6f1ea4e2f96eda6113810f37c42e49177e18961f
Author: Maksym Iarmak <email address hidden>
Date: Mon Mar 3 17:37:29 2014 +0200

    Separation of tests by folders and gate-docs fix

    For unittests was created new directory and all such tests were moved
    there. Also, .testr.conf was edited, where directory
    magnetodb/tests/unittests' was set by default tox executing.

    'tests.unittests.api.test_boto' and 'storage.model' were edited to back
    compatibility with Python 2.6 and README.rst was updated with actual
    values (stackforge) as well.

    Also, 'sphinx' support was added.

    Change-Id: I5d182644f692f4ca874185139cb72990040215eb
    Closes-Bug: #1287144
    Closes-Bug: #1287187