Renamed test file for coherence
Added "expires" attribute on ServiceView, can be set to a timedelta to control HTTP headers "Expires" and "Cache-Control".
Added some documentation about ServiceView.expires
Expires headers for Transport RTI view
Updated documentation for variable expires
Expires can handle a timedelta or a datetime
Use Werkzeug http_date for date formatting rather than custom code
Add expire headers after making the response

Avoid adding expire headers as CORS headers might return HTTP 400
Updated tests with mocked date
Merge pull request #20 from ox-it/serviceview-expire-headers

ServiceView: caching headers support