move nav to service and close mobile after routing

Objective

Have mobile nav close when the user clicks on a route

Features in this mr

• Removed all the logic checking for the window width to the main nav service
• Added a piece of state telling whether the nav is mobile or not
• Added a subscription to router events that checks the window size and closes the nav when a user routes on mobile

Further Exploration

• I think there is an opportunity here to use more observables in the constructor. But I don't want to beat this MR into the ground without getting some feedback on that first.

Closes #100 (closed)