Use the minimal width of items instead of the size of the first item for calculation of the columnWidth

Hello.

I noted, that blocks arranged in one column if the first element is not the narrowest and parameter columnWidth is empty. I fixed it in my commit.

Please, pay attention to these examples:

http://jsfiddle.net/7ZVb7/413/ - not correct variant
http://jsfiddle.net/7ZVb7/414/ - improved variant with my changes in library

Best regards.