Remove 12 hour subtraction from computeEnd func

When updating an end date directly, the computeEnd function was subtracting twelve hours from the provided value, which moved it into the previous day (since the value comes in as 12am).

The d.setHours that already existed presumably does everything that the subtraction was intended to do.
Merge pull request #17 from cebjyre/master

Remove 12 hour subtraction from computeEnd func