Here's the idea: under the `Rocket` namespace should live things critical to
writing simple Rocket apps: Request, Response, Error, etc. Nothing should be
nested more than one level deep. Only items required for more complex things
(implementing uncommon traits, etc.) should be nested one level deep.
This commit is the first attempt at realizing this.
Okay, so, given a URI, we can figure out which route is corresponds to.
Unfortunately, the handler is not yet part of that route, and we're not parsing
the parameters from the path quite yet. But, we're almost there!