I'm not particularly satisfied with the solution here. Maybe the answer
is "more middleware," but I'm not sure.

This fixes up the last few compilation errors caused by the UrlParams =>
URLParams rename.

The "name" parameter was originally a workaround for the fact that function
pointers in Go never compare equal to each other (unless they are both nil).
Unfortunately, this presents a pretty terrible interface to the end programmer,
since they'll probably end up stuttering something like:

    mux.Use("MyMiddleware", MyMiddleware)

Luckily, I found a workaround for doing function pointer equality (it doesn't
even require "unsafe"!), so we can get rid of the name parameter for good.

This change replaces a bit of API surface area (the Sub() method on Muxes) with
a slightly more expressive pattern syntax. I'm mostly doing this because it
seems cleaner: the "*" gets to take on a meaning very similar to what it means
in Sinatra (without growing regexp-like middle-of-a-path globbing, which sounds
terrifying and not particularly useful), and we get to nuke a useless function
from the API.

I guess I forgot to test it after changing it to an Insert()

I'm totally not making fun of any social networks. Promise.