added maxColWidth parameter

Hi,

I forked your (very nice) plugin and added a new parameter "maxColWidth", basically to use it more flexible in fluid / responsive designs.

Culumns "grow" to maxColWidth. When the parent container gets larger new columns are added.

eg. 
maxColWidth =500 & container=400 => one colum of 400
maxColWidth =500 & container=600 => two colums of 300

Regards

Bart