Small fixes for IE10

Wodo.TextEditor does still not completely work after this, but at least better then before.
Also makes ViewerJS in IE properly display ODT with annotations.

Any IE lovers around to continue this work? I somehow feel unmotivated for more ;)
My initial thought is a blanket rule is best. ``parentNode`` is equivalent to ``parentElement`` for all practical usages, but for the former, it is guaranteed to be on every node type we need.