Feature/add hocr to daisy script

[scottbarnes]

Add hocr -> DASIY generation.

NOTE: This requires installing with [daisy] (e.g. pip install "archive-hocr-tool[daisy]").

Some issues:

• In addition the hocr file dependency, this also still depends on _meta.xml and scandata from Internet Archive;
• There is incomplete language compatibility with tesseract;
• This isn't compatible with Python 3.6 (though from __future__ might take care of much of that);
• The module situation needs improvement (as seen by by the sample invocation)

How to run:

hocr-to-daisy -f /home/scott/Downloads/daisy/items/enqphilosophical00burkrich/enqphilosophical00burkrich_hocr.html \
-i /home/scott/Downloads/daisy/items/enqphilosophical00burkrich \
-n enqphilosophical00burkrich \
-d enqphilosophical00burkrich \
-o test_daisy_output.zip

[MerlijnWajer]

Thanks, merged!