[67174444] Adding dashboard view page + endpoint

In this pull request, I have:
1. Added the dashboard view
1. Added `PagesController` to serve our static endpoints, including the dashboard
1. Controller specs for dashboard endpoint
1. Refactor some views to use HAML pre-processing instead of ERB
1. Refactor `SessionsController` specs - in the future, I'll be sure not to step outside the bounds of the story