Twitter Bootstrap: No margin between columns

I want to remove the margins between spans in bootstrap.

One idea would be to just overwrite the css properties with zero margin and padding. Here is an example: http://jsfiddle.net/kKEpY/3/

Without the exception that the left column floats into the the right one it would work but I would prefer a direct bootstrap solution. So does bootstrap provide a property which clears the margins of the columns (span-fluid)?

Regards