handleMouseWheel fix

Fix for handleMouseWheel setting a negative scrollTop
Conflicts:
	slick.grid.js
'render' not rendering frozen rows fix

Render() was not rendering the frozen rows when the grid had been scrolled and then the frozen options set
Conflicts:
	slick.grid.js
scrollcellintoview fix

ScrollCellIntoView was returning on occasions it shouldn't
Conflicts:
	slick.grid.js
Add pgUp pgDn functionality

Page Up and Page Down functionality were removed with the 'freeze' branch. Re-implemented
Conflicts:
	slick.grid.js
Add 'active' class to active row
Conflicts:
	slick.grid.js
Fix for paging and scrolling
Conflicts:
	slick.grid.js
Update slick.grid.js
Conflicts:
	slick.grid.js