col.spanX should be display: table-column and float: none

Created by: gustavohenke

Hey, I think that the col tag should have the following CSS, when it has any of the .spanX classes:

display: table-column;
float: none;

Otherwise, it isn't possible to handle the column widths via col tags.

I know that you guys don't like supporting the grid classes within tables, but I've looked for examples of col.spanX in the BS docs, and they were there.

Tested in Windows 7 x64, Firefox@18.0.2 and Chrome@24. UPDATE: this is happening with BS 2.3.0 and 2.2.2.