Fixed issues with TurboLinks and automatically add a button if not set in options

Fixed issues with timepicker when using Rails TurboLinks applications (similar to https://github.com/jquery/jquery-ui/commit/f20486d1231fce4a559bc70f0595a071e9efc59b).
Automatically add a button if showOn is 'both' or 'button' and button is not explicitely set (similar to jquery ui datepicker).