* Move ApiController to Api/BaseController

* API controllers inherit from Api::BaseController

* Add coverage for various error cases in api/base controller

* Redirect to streaming_api_base_url

When Rails receives a request to streaming API, it most likely
means that there is another host which is configured to respond
to it. This is to redirect clients to that host if
`STREAMING_API_BASE_URL` is set as another host.

* Use the new Ruby 1.9 hash syntax