Liquid contents in simple modal

[marquex]

HI Eric,

I have made some modifications to the plugin to allow the contents have liquid widths, like 100% or 8em.

I have add a new option to the plugin 'liquidWidth' that accepts width values like '90%' so the simple modal will adapt to the window when the autoResize option is set.

Here you have the changes. Maybe you can improve it.

marquex@6d5324e

Cheers
Javi