Add region attr to zone in the GCE driver.

Closes #403

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
GCE: Add missing snapshot attributes

Signed-off-by: Sebastien Goasguen <runseb@gmail.com>

This closes #401
Merge branch 'trunk' of https://git-wip-us.apache.org/repos/asf/libcloud into trunk
Don't require paramiko when running tests with pypy.