--spit use cases into normative and informative
--added simple normative description and use cases
Merge pull request #20 from tripzero/master

Availability API and some error corrections
Merge pull request #21 from occops/master

--spit use cases into normative and informative
Merge pull request #22 from tripzero/master

changed a little bit of the wording of some descriptions
Merge pull request #23 from tripzero/master

clarified VehicleInterface API
--added group name and url for publishing
Merge pull request #24 from occops/master

--added group name and url for publishing
added section to abstract about potential sources of data