Brunnhilde

- Supports relative paths for source and destination

- Adds setup.py file and pip packaging
- Code refactor to fit code into a main() function

- Improves regex handling of PUIDs to write links to PRONOM pages for all PUIDs, including those listed as potential options for unidentified files

New features:
- User can now choose hash algorithm (md5, sha1, sha256, sha512)
- Siegfried warnings no longer printed to HTML report by default (this is to keep report size reasonable. To include Siegfried warnings in this report, pass the -w or --showwarnings flags to Brunnhilde)
- New, more readable display of duplicate files in HTML report
- Python 2 and 3 compatible (tested with 2.7 and 3.5)

Replaces deprecated apps.nationalarchives.gov.uk PRONOM URIs

- Important bug fixes re: spaces in file paths and bulk_extractor