Rackspace-monitoring

* Use service catalog to determine the API endpoint url.
* Allow user to specify auth token which is used for authentication by
passing `ex_force_auth_token` variable to the constructor.

Note: if you specify `ex_force_auth_token` you also need to specify
`ex_force_base_url` which must contain a full url including a tenant id
(e.g. `https://monitoring.api.rackspacecloud.com:443/v1.0/12345`)

* Add fetch_data_point method
* Add support for entity filtering on alarm changelog lis
* Add create_agent_installer method

* Add new agent related methods.
[Ryan Phillips]

* Remove `ex_delete_children` argument from the `delete_entity` method.

- Fix a bug with forcing base_url in the driver constructor.
[Jessica Lucci]

* Add get_monitoring_zone method.
* Add ex_traceroute method.

* Fix agent token creation.
[Ryan Philips]