Mousetrap key bindings

* Switch modal to use Mousetrap for “esc” rather than custom binding
* Bind to “c” globally for creating a new application
* Bind to “#” when the app modal is open to delete the app
* Remove NewAppButtonComponent; it’s just a simple button
* Create “Marathon” component, which is the root of the application
* Move control of the new app modal into the application rather than
  the button (a button shouldn’t own a modal)