updated code for column-count
Column count CSS changed to match naming conventions

column-two, column-three and column-four change to column-2, column-3
and column-4 to match CSS naming conventions. As this is not a popular
feature and only works in IE9+, there isn't much uptake on it yet so old
CSS names removed. No legacy support provided as it's new as of WET 3
anyhow.
Merge pull request #1446 from cfarquharson/master

updated code for column-count as there is new CSS.
Fixes gh-1149