Changed how we calculate duration from width so it will always round up ...

I calculate the "durationFromWidth" now using Math.ceil to round up to nearest multiple of 15. Hopefully in future if we change widths again this will help us avoid weird rounding issues. 

To test:
Create a new event, drag the right handle before doing anything else. Make sure time and data update appropriately. 
Check same for left bar. This was not broken before but might be now.