Fix for #117: use Khan Academy redirect URL to get latest videos.

Needed to capture the redirect for ourselves, so we could append `output=csv`.  Also added code to detail what changes have been made.

Note that the bugs in the output (reversed `added` and `removed`; spacing is weird) have been fixed.

![screen shot 2014-04-16 at 8 22 59 am](https://cloud.githubusercontent.com/assets/4072455/2721489/c706af7a-c57b-11e3-9765-92c9f4150c1f.png)

Goal is to get this in with a central server change ASAP, both because we have hundreds of dubbed videos we're not making available to our users, and because we have a specific partner who is asking for these to be updated.

@aronasorman Time for a looksie?