Introduce a toolbar with buttons

Add an Add button adding a new activity to the collection

Fix the error handling from fetching the activity collection
Update the total activities duration when a new activity is added

Update th etotal count directly instead of re-rendering the entire view
Append a button to delete an activity to every row

Delete a model behind an activity row view on clicking the deletion button
Use glyphicons and aria helpers for the buttons
Prompt for the new activity data by a modal dialog

Add a utility method for parsing time (hh:mm) to the minute count

Introduce a modal dialog for adding a new activity

Make the toolbat Add button open the dialog