Register and subsequently log in with social media accounts

Users can log into the system using their social media accounts.

This should be possible by installing and configuring a module like [Social login](https://www.drupal.org/project/social_login).

@GilesGibson which social media platforms do you feel would be most appropriate? The big three are probably:

* Facebook
* Twitter
* Google

But there are some others which might appeal to users for various reasons:

* Windows Live
* YouTube
* Reddit
* Pinterest
* LinkedIn
* Instagram
* Foursquare