Python 3 compatibility

[sebastian-nagel]

This library does not run on Python 3.x:

• along with minor syntax fixes
• the warc module dependency needs a change, cf. Python3 Compat internetarchive/warc#25, Changes to make library compatible with Python3. internetarchive/warc#26, erroneousboat/warc3

[hungrymonkey]

I am just here to document the obvious. I know this issue has already been known.

https://mail.python.org/pipermail/python-ideas/2009-March/003821.html
https://stackoverflow.com/questions/9047745/where-is-the-builtin-module-in-python3-why-was-it-renamed

Traceback (most recent call last):
  File "print_all_urls.py", line 3, in <module>
    import warc
  File "/Users/psuedofinnish/git_repo/engage-warc-test/venv/lib/python3.7/site-packages/warc/__init__.py", line 10, in <module>
    from .arc import ARCFile, ARCRecord, ARCHeader
  File "/Users/psuedofinnish/git_repo/engage-warc-test/venv/lib/python3.7/site-packages/warc/arc.py", line 7, in <module>
    import __builtin__