Auto-adjust for IE7&8

[ywarnier]

Add a check for IE7 and IE8 and an automatic change of display params.
This relates to #13, where you have to apply a (small) patch to make the frame exist in IE7&8. This takes place in the iframe tag line, in jquery.printPage.js, just below:

var components = {
iframe: function(url){

Low priority, obviously, but this might improve it for many not reading the issues list.
Thanks for this great plugin!