Add a new option appendWidgetTo

Added a new option to timepicker allowing for custom placing of the modal widget.
This was needed because of IE7.

There is a gist with the HTML needed to reproduce the error.

https://gist.github.com/pedroma/4961018

After applying the changes in this pull-request if you initialize 
$("#myModal input").timepicker({appendWidgetTo:"#myModal .modal-body"});

and it works.