Prevent un-necessary events in ColumnResizer
When a column is first resized, the `resizeColumnWidth` method is called on all columns in the grid. This was causing the "dgrid-columnresize" event to fire on unaffected columns. This change prevents these events from being emitted.
Merge pull request #459 from msssk/columnresize-event

Fix #441: Prevent unnecessary events in ColumnResizer