Allow botdylan to use oAuth authentication to the GitHub API

Basic auth is the default, but the user can specify `auth: "oauth"` and
`password: "OAUTH_TOKEN"` in config.json to use oauth.

make basic auth the default

allow for either basic or oauth authentication

update README to add auth key to config.json section
Merge pull request #9 from grahamb/oauth

Allow botdylan to use oAuth authentication to the GitHub API as an alternative to basic auth