Update rendering to handle :focus styles (IE8)

[lojjic]

Reported by RwwL in a comment from issue #36:

• :focus styles (say, a border color change) on the input are not applied until keydown or until the cursor is moved off the field
• if you tab or click away from a field after its focus styles are applied, the focus styles are not removed until I mouse over the field again

It should be noted that :focus is not supported at all before IE8. We might consider making PIE add a custom class to focused elements which would allow stylesheets to use that class rather than :focus to get the same effect in IE6-7.

[jasonmp85]

Is it necessary for PIE to emulate :focus behavior for IE6 and 7 when something like Selectivizr already takes care of this emulation? I think the low-hanging fruit lies with the rendering issues. IE 6 and 7 can gracefully degrade for all I care, but IE 8 is glitchy. How tough is this bug to crack? The rendering appears to take place, but it doesn't appear until I hover over the :focused element.

It should also be noted that :active suffers from the same issues. As :active is pretty useful for styling links and input[type="button"], it should probably also be addressed.

[lojjic]

This should now be fixed, see the above commit.