Add support for old school apis (v1.5)

Add a version attribute to options, default value is set to v2.
Update login method from Client class to add v1.5 support
Update send_message method from Messages module to add v1.5 support
Merge branch 'topic/am_add-support-for-old-school-apis' into develop
Bump version to 2.0.2 for release
Merge branch 'develop'