'Done' action dispatch when finishing a workout

[mbosselut]

When doing a workout, the 'Done' button should call a new action (through the finishWorkout function) to remove this workout from the todaysWorkouts array. That way the next 'Start your workout' call through the dashboard will correctly launch the second exercise of the day.

Once todaysWorkouts is empty, a PUT request should be made to :userid/calendar/day to add that user as having completed this day's workout