Position the scroller higher if a footer exists.
Use the offsetHeight of the footerNode if it exists.
Add ColumnSet test to Pagination test page
Only execute a remove call if the remove handler exists.  If a column is already hidden, don't try to hide it again.
Note ColumnSet + footerNode fix in CHANGES.md
Merge pull request #466 from SitePenMatthewMaxwell/ColumnHider

Fix #464: Only execute a remove call if a handle exists.

If a column is already hidden, don't repeat hide logic, otherwise it can't be re-shown.
Note ColumnHider redundant-toggle fixes in CHANGES.md