Select repo

[mdaffin]

Once a user has signed in they will need to pick a repo to load/access. Their selection should be stored in local storage so that we don't need to ask them again when they next visit the page - or just reload the window.

Path: /repos/

Redirect to this page if they are logged in but have not already picked a repo.

This initial implementation only need to load a single repo, future implementations will allow for multiple repos to be selected.