Handle edge case for "self-paced" courses

Some courses are self-paced or asyncronous, where there is no specific
time.  To handle these, for now we are just keying them in with a start
time of 12:00am, and using that to trigger a "date only".
Merge pull request #10 from cit-jmu/allow-blank-start-time-for-parts

Handle edge case for "self-paced" courses