WIP: Add new enrollment message to the dashboard

This is related to the Destination edX Story: https://openedx.atlassian.net/browse/ECOM-403

Attempting to pipe through the newly enrolled course ID and display it as a notification on the Dashboard. This is still a *work in progress* and needs testing, URL encoding, etc. 

Putting this up so we can discuss alternative solutions that may be more elegant and less prone to error. 

Here's a screen shot of this, as-is:
![image](https://cloud.githubusercontent.com/assets/235752/4444488/42df33ea-47f1-11e4-81fb-58b75622d0fa.png)

@wedaly @dianakhuang @rlucioni @marcotuts  FYI this is not for review, just informational. 
I wonder if it makes sense to make `5` here a setting instead of something hard-coded in.