resolving dialog blocking elements

## Resolves
* Issue https://github.com/fabien-d/alertify.js/issues/92

## Notes
* Moved common elements to be fetch only once per dialog (buttons, form, input)
* Fixed `transitionend` events
* Create common `setFocus` private method instead of repeating code
* Hide dialog after fading out (fixing the raised issue)
* Replaced IE7-8 CSS hack. Turns out IE10 reads it `\9`.