Version 2.0.0-alpha.1

This is a whole brand new tartufo! It's been entirely restructured, rewritten,
retested, rebuilt, and remade! It's now more extensible, readable, testable,
and usable.

New features include:

• #2 - Verified/approved exclusions are now handled by way of hash signatures.
  • These hashes are created on a combination of the matched string and filename
    where the match was found. They are generated using the BLAKE2 hashing
    algorithm. (via #61)
• #7 - A working directory can now be specified to clone to when scanning a
  remote repository. (via #81)
• #11 - Removed the --cleanup option and added a --output-dir in its place.
  Issues are now written to disk only when specifically requested by providing
  an output directory. (via #82)
• #39 - The functionality is now split into sub-commands (via #78) Available
  sub-commands are, for now:
  • pre-commit
  • scan-local-repo
  • scan-remote-repo
• The entire library has been refactored and nearly all logic has been put
  into its most appropriate place. It should now be possible to use this whole
  tool as a library, and not just a CLI application. (via #29, #65, #67, #70)

Bug fixes include:

• #55 - The tests no longer iterate over this repository's history; everything
  has been sufficiently split out to make it more testable without needing to
  look at an actual git history. (via #70)
• #72 - Specifying a non-git path no longer causes an error (via #80)

Other changes:

• Issues found during the scan are now represented by a class, instead of some
  amorphous dictionary (via #29)
  • Further, since a single Issue is instantiated per match, the output key
    for the matches has changed from strings_found to matched_string.
• #25 - Set up full documentation on Read The Docs (via #38)
• #30 - Support for Python 2 has been dropped (via #31)
• #58 - CI is now handled by GitHub Actions (via #59)