Fixes Github Mapper route

[404-geek]

The github mapper function (minecode/mappers/github.py) is having issues where the github urls fetched in run_visit command are not able to parse and are failing to get added into DB.

This is because of the improper router regex in the mapper file.

@map_router.route('https://api.github.com/repos/[\w\-\.]/[\w\-\.]')

The below regex url is able to parse the urls successfully

@map_router.route('https://api\.github\.com/repos/([^/]+)/([^/]+)')