Includes additions to User, Organization, Repository, and Gist.  Some
minor changes to existing fields based on changes in the v3 API (for
example, Gist.User became Gist.Owner).  Most everything else is new
additions.

refs #103

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!

Apply gofmt

This includes all of the methods mentioned in this blog post:
https://developer.github.com/changes/2014-03-18-paginating-method-changes/
as well as a handful of others I found.  Sadly, this is a breaking
change for many of these methods because it changes the method
signature, but with yesterday's API change these methods are now broken
anyway. :(

it's not the cleanest, but it works.

instead of inspecting the JSON tags on the struct fields directly,
actually run it through JSON marshalling and unmarshalling, then compare
those results.

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.

- ListCodeFrequency
- ListPunchCard

- use Timestamp for Week fields instead of int
- rename WeekHash to WeekStats

So it appears GitHub already supports multiple types of subscriptions:
repositories and threads.  I'm leaving the data type simply as
'Subscription', but am updating the method names to avoid confusion,
since they're both part of the ActivitiesService.

mark RateLimit method as deprecated in favor of RateLimits which returns
both the core and search limits. (see deprecation notice in API docs:
https://developer.github.com/v3/rate_limit/#deprecation-notice)

depending on who people are using rate.Reset this may or may not be a
breaking change, since Timestamp supports all of the exported methods
from time.Time.

this is a breaking change, but this was only recently added so I'm not
too worried.  This also seems the best way to handle sub-namespaces on
this method.