Fix for CommonJS/Browserify

I'm not sure whether this breaks any other CJS implementation, but the only one you're likely to have to worry about is Browserify.

This relates to https://github.com/DataTables/DataTables/issues/434
Fix #23: Attach the scroll event for the header alignment using the `DT` namespace to ensure that it is removed on destroy
Merge pull request #22 from bjmiller/master

Fix for CommonJS/Browserify