Adding TravisCI configuration, badge, GoDoc badge.

...oops. "[]" are brackets. "{}" are braces.

Instead of returning awkward untyped error strings, return real error
structs. This will allow users of the library to extract interesting
semantic meaning from our errors, and is just all around less awful than
what we had before.

Previously, we disallowed setting the empty string as a key in a map,
since at the time it seemed like doing so would allow all sorts of
unsavory bugs. In practice, I think this probably isn't actually true,
as I wasn't able to think of a scenario in which this bug would
materialize during the several moments I thought about it.

Plus, the code here to do sanity checking was wrong anyways.

They're really verbose. I should probably DRY them up later.

httptest was adding an extra flag, which was sort of ugly. Instead,
reimplement the parts of its functionality we were using. Bonus: due to
specialization, it's now a bit more efficient as well!

graceful.Server was made private in 05c2ca7e, but I think the increased
flexibility you get with being able to provide your own TLS options
(etc.) outweighs the API complexity of an additional type.

This bugfix brought to you by `go vet`

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.

Wonder how long those have been there.

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.

These were introduced by breaking changes in the following commits:
- aca58b22cf (ValidMethodsKey)
- 386323a6ed (HTTP methods are case sensitive)

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

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

Who knew! (RFC 2616, 5.1.1)

For sendfile(2) support. I should really DRY up the implementations here...

In order to avoid a dependency on the go.crypto terminal package, let's try to
do our own TTY sniffing. I think in practice this will work surprisingly well,
even if it feels incredibly sketchy.