listen for scroll events on targets' scrollable parents
implemented more comprehensive DOM transversal solution with group option
resolved merge conflict
Merge branch 'scroll_fix' of github.com:HandyAndyShortStack/jquery-sortable into oddbird-test

* 'scroll_fix' of github.com:HandyAndyShortStack/jquery-sortable:
  resolved merge conflict
  implemented more comprehensive DOM transversal solution with group option
  listen for scroll events on targets' scrollable parents

Conflicts:
	source/js/jquery-sortable.js
typo fix
Add better support for touch devices.