Docker-fabric

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* Fixed side-effects of modifying the ``base_url`` for SSH tunnels, causing problems when re-using a client returned
by the ``docker_fabric()`` function (`Issue 12 <https://github.com/merll/docker-fabric/issues/12>`_).
* Added ``version`` method to CLI client.
* Added ``env.docker_cli_debug`` for echoing commands.
* API clients' ``remove_all_containers`` now forwards keyword arguments.

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* Added Docker-Map's new features (keeping certain tags during cleanup and adding extra tags during build).
* Added experimental :ref:`cli_client`. This has changed the module structure a bit, but previous imports should still work.
From now on however, ``docker_fabric`` and ``container_fabric`` should be imported from ``dockerfabric.api`` instead
of ``dockerfabric.apiclient``.
* Fixed installation task for CentOS.

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* Updated Docker service installation to follow reference instructions.
* Added separate utility tasks for CentOS.
* Fixed build failures in case of unicode errors.

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* Client configuration is not required, if defaults are used.

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* Implemented local (faster) method for adjusting permissions on containers.
* Fixed issues with non-existing directories when downloading resources from containers.

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* Minor logging changes.
* Make it possible to set raise_on_error with pull (`PR 3 <https://github.com/merll/docker-fabric/pull/3>`_)