0.6.1

Major contributions by @mlbright, @fzs, and @ArturKlauser.

New functions:

* List organization
* External collaborators
* List all users
* Edit releases
* List public and user gists
* Show a single gist
* Fork a repository
* List webhooks

MIME support additions:

* JAR
* WAR
* APK

Bug fixes:

* Handle "100 Continue" HTTP response

Documentation:

* Add examples for downloading release assets

New environment variables:

* `GITHUB_TOKEN`