fixes #21 on the cnxml to html5 side. Warning: New HTML to CNXML for this spans is not included here!
make span not self closing when no children
use data-media-type instead of data-mime-type
Merge pull request #22 from Connexions/web-and-print-images

fixes #21 on the cnxml to html5 side. Warning: New HTML to CNXML for thi...