LIBCLOUD-625: Allow for internal GCE authorization with metadata service
Allow users to pass "headers" and "method" argument to the get_response_object
utility method.
Use assertEqual instead of the deprecated assertEquals

Closes #375

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Bump versions for 0.16.0 release.
Merge branch 'trunk' into LIBCLOUD-625_gce_auth_internal

Closes #376
Update CHANGES.
CLOUDSTACK: Minor fix for start-vm option

Closes #377

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