Fixes #420
Closes #423

Fixes #397.

Change-Id: I30ce336e3a36cf5758b9bf52b9dd77f7c1df5f27

Note that this is an API-breaking change but should have minimal
impact on users of this package due to the nice inference
properties of the Go programming language.

Bumped `libraryVersion` to `2` due to API-breaking change as
discussed in #376.

Fixes #180.

Change-Id: Ib386135e6b8f306d1f54278968c576f3ceccc4e7

Fixes #152.

Add tests for RateLimitError.

Refactor populateRate into a more general parseRate.

Rate is now a method, not a field.

Mention RateLimits rather than RateLimit since the latter is deprecated.

Use Go convention for marking deprecated identifiers. See
257114af91.

First draft, suggestions for improvements are welcome. The snippet
should serve as the idiomatic guide on how to get all pages for a given
resource (a common use case without an obvious solution, hence the docs
can be very helpful).

- minor updates to README
- expand package docs to include more information on authentication, as
  well as new sections for rate limiting and setting pointer values.

our package docs are too long yet to really need to be in their own
file, but I'd like to flesh them out a bit more, particularly once #19
is resolved.