Added PDF Annotator plugin as dtm.coffee.

Revision 631c1345215cdcceecbe35a69da9f59ae35e4c07 from branch
typed-packaging in hypothesis/annotator fork.
Track current page (currently shown page) number.
Integrated dom-text-mapper. Thanks @csillag for all the help.
Renamed our annotator to highlighter.
Renamed annotator file to highlighter file.
Integrated Annotator.