Stop lowercasing everything.

Case-sensitive routing, I _guess_.

Also, fix error checking from golangci-lint.

Fix Router to not require a pointer.

Make a bunch of Router's methods act on a non-pointer, as they don't
need the pointer and it makes using it as an http.Handler easier.

Rewrite for 2.0.0!

This is basically a ground-up rewrite/refactor. A lot of more
complicated code was rewritten to use types that make it clearer and a
lot less fragile. We changed the trie around a bit to the point where
I'm not sure if it counts as a trie anymore, but we're no longer
mingling static and dynamic path elements, which makes everything much
clearer. We're also termining endpoints and prefixes with a special nul
node in the trie, to make it clear when the full thing has been matched.
The nul node is also what gets methods on it, which makes things a bit
more straightforward.

We now also have executable and testable examples, which is cool.

v1.0.1: patch release.

Fix two bugs: first, when dealing with different child routes with a
common ancestor, correct how the route trie gets constructed so all
child routes actually match. Second, when calculating the priority of a
matching node to decide which node to use as the result, calculate the
ancestors' priorities recursively, and add them to the current node's
priority. This is a change from how it was done previously, where only
the immediate ancestor's priority was considered.