New functionality for counting TFRecord examples

[monocongo]

Resolves issue #143

[codecov]

Codecov Report

Merging #144 into master will increase coverage by 0.24%.
The diff coverage is 28.57%.

@@            Coverage Diff             @@
##           master     #144      +/-   ##
==========================================
+ Coverage   54.25%   54.49%   +0.24%     
==========================================
  Files          17       17              
  Lines        1211     1224      +13     
==========================================
+ Hits          657      667      +10     
- Misses        554      557       +3

Impacted Files	Coverage Δ
src/cvdata/__init__.py	100% <100%> (ø)	⬆️
tests/test_analyze.py	100% <100%> (ø)	⬆️
src/cvdata/analyze.py	46.46% <18.91%> (+2.64%)	⬆️

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