Better Named Routes

As brought up in #3, our routes are very bad. I'd recommend we push for a REST-style of URL names.

When signing in, the URL should not be `/sign_in`, but `/sessions/new`. (This does exist currently, but we persist in using `/sign_in`.) What's really on the table here, then, is that we drop these silly name conventions that we have and instead standardise on REST verbs for our names.