Merge pull request #64 from octokit/jingweno/go-sawyer

Point to a fork of lostisland/go-sawyer
Add Commit struct
Add commit APIs
Implement CommitService#Patch

This API is to get a commit patch. It returns a read IO and the response result.
Check nil of result.Response
Merge pull request #66 from octokit/commits_api

Adding commit APIs
Merge branch 'master' into gist_api
More generic `getBody` method with configurable media type

This is so the same method can be used with "text/plain" content type,
for instance.
Add `Raw` method to Gists for fetching gist content

It first scans the list of files in a gist from GitHub API and then
follows the raw url of the first file using "text/plain" content type.