Groupby ported to nim

[omenSi]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 78.12500% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 82.49%. Comparing base (ab32d28) to head (f11cc68).

Files	Patch %	Lines
tablite/pivots.py	53.33%	7 Missing ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #158      +/-   ##
==========================================
- Coverage   82.98%   82.49%   -0.49%     
==========================================
  Files          27       26       -1     
  Lines        4072     3884     -188     
==========================================
- Hits         3379     3204     -175     
+ Misses        693      680      -13     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[realratchet]

Ship it, although we might want to change .toFloat() in the future since it's now used in few places.