Bugfix with contextmenu positioning

The first time the contextmenu is being positioned it would not take into account its real width and height, those after the rendering of its template.

Working in IE8

This release includes updates for the context menu to work normally in IE8

Minor adjustment on user experience

Using "mousedown" instead of "click" on closing context menus

Version 0.1.3

If the context menu is rendered outside the window's viewport then adjust its position accordingly.