Make plugin name clickable in the plugins tab

`discourse-omniauth-gitlab`'s name in the Discourse plugins tab appears non-clickable.

Adding the URL as a comment fixes that.

See merge request !4

Bump omniauth-gitlab and plugin versions



See merge request !3

added ability to connect existing accounts

The old code only authenticate if user already has gl_uid in the plugin store, now if the user does not have it and tried to login with gitlab, it checks if there is any user with the same email as gitlab, adds gl_uid for that user then logs in.


See merge request !2

Just store the secrets in app.yml

This reflects what I ended up doing on forum.gitlab.com.

See merge request !1