Issue title: Document necessary oauth scopes
 Issue body: It's awesome that I can choose to authenticate with a personal access token, but it would be _even awesomer_ if you provided a guide for which scopes the application needs :)
 Comments: 
 Comment 0: This was actually very [well documented](https://github.com/donnemartin/gitsome/blob/master/COMMANDS.md#gh-configure)! It was even referred to in the install instructions (only under "Github Enterprise users", which was why I didn't notice it).
{'source': 'GithubIssues', 'repo_name_with_owner': 'donnemartin/gitsome', 'issue_id': 189453192, 'repo_stars': 7963.0}