WIP Awais786/course info api

@stephensanchez    We have implemented initial api workflow.  Can you please take a look ?

following is api url.
/api/courseabout/v1/course/about/[course-id]
You shouldn't need this. CourseKey extends OpaqueKey, which, if no key is found for the serialized format, will check for a deprecated format as well. 

It's still worth checking for an InvalidKey, though, if none is found for a regular or deprecated string.