Logger: Add possibility to send sync requests.

In this PR was done:
 - `*.coffee` -> `*.js`;
 - added possibility to set request parameters;
 - fixed and added new jasmine tests;
 - removed unnecessary `Courseware.prefix`.

@mulby, @andy-armstrong  please review.
I think you should probably catch and report exceptions from the callback so that a failure doesn't cause the event not to get logged.