[vim] Update vim visual mode selection to match CodeMirror selection

Remove off-by-one in vim when head is further forward in the document than the anchor, where vim's selection becomes 1 less than CodeMirror's. This was originally done because the cursor showed past the anchor and looked like an additional character selection.
[vim] Update LastHPos in visual only if not infinity
[vim] Added CSS3 animated fat cursor
[vim] Polish css3 animated fat cursor