Get default width from css media queries

[RangerMauve]

• inside windows.js before we invoke .show
• invoke js in the page that does the following:
• list through all the stylesheets
  • find css rules for media query breakpoints
  • find css rules for max-width on the body or html
• find the smallest referenced width that's less than whatever the default window width is
• set the window width to that
• then show
• if no widths are found use the default
• This shouldn't be done if the width is know from the constructor options