Updated docs for v2

[tarkatronic]

This is, hopefully, the last thing needed in the lead-up to v2.0.0 final!

Fixes #74
Fixes #75

This ended up, largely, being a rewrite and cleanup of the documentation. The hope is that the structure overall makes more sense and information is more readily available, easier to find, and automatically up-to-date.

I added 2 Sphinx modules:

• sphinx-click -- This automatically extracts the full usage of the click command, for the Usage document. This way we don't have to remember to copy-paste it into there every time usage changes. NOTE: This does not, however, fix that need for the README.md. Not sure what to do there yet.
• sphinxcontrib-spelling -- A spellchecker! Yay! This also meant setting up a custom word list under docs/source/spelling_wordlist.txt, for words that we know are definitely spelled right, but aren't in the default dictionary.

Possibly the easiest way to review these will be with the fully rendered version, so I've activated this branch over on ReadTheDocs (although it is hidden from the version menu). You can find it here: https://tartufo.readthedocs.io/en/v2-docs/

[codecov]

Codecov Report

Merging #111 into master will increase coverage by 6.52%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           master      #111      +/-   ##
===========================================
+ Coverage   93.47%   100.00%   +6.52%     
===========================================
  Files           9         3       -6     
  Lines         567        75     -492     
  Branches      101         5      -96     
===========================================
- Hits          530        75     -455     
+ Misses         32         0      -32     
+ Partials        5         0       -5     

Impacted Files	Coverage Δ
tartufo/scanner.py
tartufo/__main__.py
tartufo/util.py
tartufo/config.py
tartufo/types.py

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[mxhenry-godaddy]

Love the wordsmithing and things are very clear. Just a few nitpicks.

[sjacoby-godaddy]

looks great, ship it!