Created reactivation business feature

I moved deactivation into a new ‘activation’ feature file and I added a
reactivation feature. This new feature just tests that businesses can
be reactivated once they’ve been deactivated.
Added activate to businesses

I added an :activate method to the businesses controller and
corresponding specs and routes. This action simply activates a business
that has been deactivated.

As well, I setup the index view to show a link to either the activate
or deactivate action depending on whether the business is active.
Merge branch 'User-should-be-able-to-reactivate-businesses'