use requests throughout. other tweaks.

* I consolidated the various calls to the Internet onto the requests
library for simplicity's sake.
* As a result, I cleared out the json, urllib2, &c imports that were no
longer needed.
* I ended up adding some extra logic to the UrbanDictionary code, so it
won't necessarily just use the first definition every time.
* And some small changes to appease pylint, since I'm still not actually
running this code.