Add tasks for GitHub updates

[Serchinastico]

Instead of showing all the current statistics, create a task that only notifies the view whenever there has been a change on a project or an user.

[alorma]

Sadly, github doesn't provide a push notifications, but i've already implemented on Gitskarios.

If you need it, i will be happy to collaborate

[Serchinastico]

I was thinking on something as easy as a polling task with an in-memory cache. Feel free to send us a PR though!