Added logic and UI to notify the user that starting a timer would cancel/stop an existing, running, timer.
Added confirm start timer view layout.
Added handler for failure of existing timer AJAX request.
Use _.find rather than _.some to capture value of truthy element.
refactor: extract showConfirmationDialog helper
Added guard to protect against an instance of the confirm dialog already being in the DOM.
Merge pull request #5 from zendesk/stefan/confirm_start_timer

APPS-292