TODO

To process files before 1950:
- read https://www.retrosheet.org/GameFiles.pdf and decide how to handle EDx files
- fail to read any EBx or EDx files
HOWTO is getting long, make it easier to do
use Retrosheet data to figure out if a runner starts on second base in extra innings
This seems wrong:
    # Make sure we don't duplicate keys.
    # Strip off the inning info (for now?) and the curScoreDiff
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refactoring
 - performance
   - encapsulate creating an re the first time we need it
 - more strongly type things
 - events that start with 'W+' have a bunch of duplication (also 'K+'?)
duplication in processCumulativeStats and processCumulativeBallsStrikesStats