Cleanup and improve some docstrings.
Modify _connect_and_run_deployment_script to return a Node object on success.
Use better variable names, move check to the top.
Update Contributing document.
Issue LIBCLOUD-480: Add additional attributes to the "extra" dictionary of
the VolumeSnapshot object in the EC2 driver.

Also modify create_volume_snapshot method to correctly handle "name" argument.

Previous, "name" argument was used as a snapshot description, now it's used
as a Tag with a key "Name".

Signed-off-by: Tomaz Muraus <tomaz@apache.org>