Image Match Versions Save

Make cairosvg import optional, better error handling for signature generation.

Fixed a bug where some images would not compute signature correctly

• Elasticsearch 5 query compatibility
• can now specify wait for write acknowledgement on add_image.
• can check for duplicate record paths before adding

Fixed a bug related to python3 conversion

All orientations was throwing an exception since the python3 compatibility change. Now fixed.

Now Python3-compatible! Thanks @saru95 for your contribution.

Now you can save metadata with the image records.

• rework setup.py and add package to PyPi
• add dockerfile and add to dockerhub

• Implement pavlovml (non-breaking) interface changes
• Fix bug with latest elasticsearch driver

• Initial release