Move Joyent compute driver to a single class + region argument model.
docs: Update upgrade notes.
docs: Fix a typo.
Document argument type in the ec2 driver.
Update CHANGES.
Revert some changes so I can apply patch cleanly.
Modify ElasticHosts driver to take region argument (w.i.p.).

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Use super instead.
Pep8 fixes.
Re-apply reverted changes and more progress on region support in elastichosts
driver.
ElasticHosts compute driver: Use region names exposed by the provider.
Add tests for the new region functionality in the ElasticHosts driver.
Indicate which constants have been deprecated.
Use unittest2.
Update CHANGES.
docs: Update upgrade notes.