Add a github UDA for user field

[stbenjam]

This adds a gitubuser uda that gives the reporter for an issue, or the creator of a pull request. I use this in my .bugwarriorrc like the below:

This way, I can do queries like task +github_pull_request +created_by_me

[github.stbenjam]
service = github
github.username = stbenjam
github.login = stbenjam
github.token =  XXXXXXXXXXXXXXXXXXXXXXXXXXXXX
add_tags = github, created_by_{{ 'me' if githubuser == 'stbenjam' else 'other' }}, github_{{ githubtype }}
github.import_labels_as_tags = True
github.label_template = github_{{ label |lower}}
github.involved_issues = True
github.filter_pull_requests = True
github.include_user_issues = True

[mathstuf]

Might be better to word this as Author of issue/PR.

[stbenjam]

@mathstuf Updated, thanks that's better wording

[ralphbean]

Good stuff. 👍