Isolate docs changes from MABE changes in #480

[emilydolson]

A version of #480 that modernizes our documentation but isn't entangle in the MABE changes.

[codecov]

Codecov Report

Attention: 5 lines in your changes are missing coverage. Please review.

Comparison is base (fc374d2) 79.06% compared to head (155c3c5) 79.06%.

❗ Current head 155c3c5 differs from pull request most recent head e1b4c29. Consider uploading reports for the commit e1b4c29 to get more accurate results

Files	Patch %	Lines
include/emp/base/Ptr.hpp	50.00%	2 Missing ⚠️
include/emp/data/DataFile.hpp	33.33%	2 Missing ⚠️
include/emp/bits/BitVector.hpp	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #484      +/-   ##
==========================================
- Coverage   79.06%   79.06%   -0.01%     
==========================================
  Files         306      306              
  Lines       34999    35001       +2     
==========================================
+ Hits        27671    27672       +1     
- Misses       7328     7329       +1     

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