[FEATURE+REFACTOR] Changed the structure to separate the concepts. API methods and object types. Added a Member class to handle (un)subscribing. Tests for authentication too.
[STYLE] Tabs to spaces
[UPDATE] Root module namespace from ResponsysApi to Responsys
[UPDATE] Now using the client as a singleton. Cleaned up classes and updated the tests.
[TEST] Started a Member spec
[STYLE] Double quotes to simple quotes when no interpolation. Fix a require path.
[TEST] Fixes, cleanup. Added a logout test.
[STYLE] Compliance to Ruby style guide
[UPDATE] Readme with updated usage section
[UPDATE] Error in README
[UPDATE] ListMergeRule with new initializer