Allow setting a cell's min_width and max_width properties

[ericfreese]

This allows you to pass in min_width and max_width options when creating a table cell to override the default calculations.

[ericfreese]

There is still a problem here. I believe it's an old bug that is only showing itself now that a cell's max_width can be something other than @pdf.bounds.width.

It appears that max width is not taken into account when calculating a table's column_widths.

[akostadinov]

Can this be merged because it makes things somehow better anyway? For example it makes sense to set min_width of header cells to something that will not wrap the header words, e.g. Address not to become Addres\ns.