set the default closing time bases on the user's time zone 

ISSUE: The default close date in the start a new proposal form showed 3 days from now, but was displayed in server time(UTC).

This feature simply sets the application timezone from the users timezone and calls Time.zone.now instead of Time.now

Also included:
- previous dates are disabled from time picker
- close-date label is added to en.yml
- fields in for are resized to display the timezone field better.