Extra changes

Now that I have what I said I would have in my project proposal, I have
expanded the ability of University Explorer. Now you can ask more
specific questions instead of getting a 30-second-long summary. The
skill also can prompt the user a second time if it doesn’t hear
anything. I replaced every instance of NULL in my dataset to say “Not
specified” because it sounds better. Sample utterances no longer
include the test utterances that I used to start out with.