fix(uiGrid): Fix elm height calc for hidden grids

The header row height could not be calculated when the grid was hidden,
because the absolutely-positioned cells did not count towards the
container height.

To fix this, I made changes to the elementHeight/elementWidth functions
that will, if the element in question is hidden, append the element to the
document body with visibility: hidden.

I also had to switch the cells from being absolutely positioned to
relatively positioned and floated left.  Hopefully this will not have any
further repercussions
Remove console.log()
Explicitly set viewport scrollTop to 0 in link fn; FF has a bug that caches this value even for dynamically created elements
Merging Shane's cell editing changes. Making tutorial formatting consistent in style.