authoriseGitHub is function that performes OAuth authorisation with GitHub API
and stores resulting token in the github_token variable.
In order to authorise your app you need ClinetID and ClientSecret.
They can be found here: https://github.com/settings/applications/new
A 20 characters long string with Client ID. See https://github.com/settings/applications/ for more details.
ClientSecret
A 40 characters long string with Client Secret. See https://github.com/settings/applications/ for more details.
scope
A character vector with the list of availables scopes for the GitHub API token. See https://developer.github.com/v3/oauth/#scopes.
For repository deletion you will need to add "delete_repo" scope.