V 0.3:
- improvement: all modality elements will be resized.
- setting position to fixed when the popup is smaller than the viewport
- bugfix: if one of the shadowCSS properties is defined, others would not be created
- bugfix: avoid the keydown to be attacched more than one time on multiple modality on the same page
- bugfix: locate correctly the modality window when multiple modality items is used on the same page