This commit adds support for Git refs.

Listing of refs does not support sub-namespaces.

Fix to keep query string intact when 301 redirect occurs.

go fmt.

go fmt.

result of `gofmt -s -w .`.

result of `gofmt -s -w . `.

According to various blog posts of the official github developer website
[1] [2], the mime preview for Releases and Search are no longer needed.
Moreover, they recommend to use `application/vnd.github.v3+json` for
every requests.

[1] http://developer.github.com/changes/2013-11-04-releases-api-is-official/
[2] http://developer.github.com/changes/2013-10-29-search-api-becomes-an-official-part-of-github-api-v3/

Fix typo in documentation

Includes Repositories.ListReleaseAssets, Repositories.GetReleaseAsset,
Repositories.EditReleaseAsset, Repositories.DeleteReleaseAsset,
Repositories.UploadReleaseAsset.

include Repositories.ListReleases, Repositories.GetRelease,
Repositories.CreateRelease and Repostories.DeleteRelease.

this is a breaking change for a handful of Option structs that were
defining the Page option directly (they now embed ListOptions).

finishes fixing #56

this change also includes some additional minor code cleanup

fixes #58

run through 'gofmt -s'

Fix typo

remove doubly present "the"

this only updates a few user and repo functions just to establish the
calling pattern.  closes #56 (which also includes a little more
background)

ktoso kind of shamed me with his extensive resource tests in #49 :), so
I'm finally starting to setup a structure for more general testing of
this type.  This change adds the `testJSONMarshal` helper function, and
adds tests for the `User` type.  This includes two checks:

 - check that an empty resource produces an empty JSON object.  This
   effectively verifies that all fields include 'omitempty' so that
   we're not unintentionally sending additional data over the wire.

 - check that a full resource with every field populated produces the
   expected JSON.  This verifies that the JSON field mappings are
   correct.  In this case, it might be okay to use resource samples from
   the GitHub docs, though I do still prefer very simple field values
   since it makes tests easier to read.

When these tests are added for each resource type, we can reduce all of
our other tests to return bare minimal response bodies, since the
resource fields are already being tested at that point.

- 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.

Add "of" like the rest of the function docstrings