Make sysadmin dashboard gitlog date timezone-aware

@carsongee Just a small change to the sysadmin dashboard gitlog:
* Redundancy reduced in the template
* Date is timezone aware and formatted as `util.date_utils.DEFAULT_DATE_TIME_FORMAT`

Before:
-----------
![before](http://i.imgur.com/71heogf.png)

After:
--------
![after](http://i.imgur.com/GnBQvzQ.png)


Also, there's too much logic on this line. I'd suggest doing something like:
```mako
<%
if course_id == None:
    cilset = cilset[:2]
else:
    cilset = cilset[:10]
%>
% for cil in cilset:
    ## etc
```