Rewrite REST code using Requests library

[graphiclunarkid]

The current code for getting data from APIs is based on a copypasta implementation of a routine from Dive Into Python. This requires manual handling of things like redirects, etags and last-modified checks. The requests library seems to offer these as built-in features so it should be easier to work with. As a bonus, Requests has HTTP/HTTPS proxy support now too, so using it should mean implementing #2 will be easier.