Github API url is not necessary

[erodewald]

By default, GitHub and its variants include an GITHUB_API_URL environment variable, so the addition of github_api_url just increased code complexity, reduced maintainability, and actually reduced flexibility since it assumes https://. The latter meant I was not able to simply pass in $GITHUB_API_URL, because it became an invalid url (e.g., https://https://my-enterprise.url.com/api/v3).

[cscleison]

actually, if i keep the github_api_url: 'api.github.com' that comes from the example, it does not label my prs at all. it only worked after i omitted the line. it took me quite a while to figure it out 😄

[rubeeengm]

actually, if i keep the github_api_url: 'api.github.com' that comes from the example, it does not label my prs at all. it only worked after i omitted the line. it took me quite a while to figure it out 😄

Nice!

[johnlk]

There were two potential issues:

1. the readme example excluded the http:// which would break if copied
2. github enterprise accounts have to set a value, which shouldn't be required

Both have seen been addressed by #57 and #62 respectively.