Bug Fix around check if object is window

Changed code to use jQuery's $.isWindow() method for determining if the given element is the window object.
Bug fix

Changed check for window object to correctly set references if NOT window
Support for setParentOnStick option

Support for setting the heigh of the stickOnScroll element's parent node, so that natural page flows is not disturbed.
Support for items with margin values set

Element that have a margin-top value set are now properly displayed when stickOnScroll is triggered.
Bug Fixes

- Fixed position offset issue when original sticky element is moved on teh page (ex. elements are inserted above it)
- Support for making element sticky even if they are initially hidden.