Add Yo plugin

Here is a plugin providing support for justyo.co.

I'm unsure whether or not there is a broad enough appeal to consider adding this, but wanted to try as it would have some value for us.

Also unsure whether or not the process is clear, from Yo's documentation, for devs. People who want to be notified should Yo at the development Yo account, and in turn all of these subscribers will receive Bugsnag notifications.