some small repairs

[haberdashPI]

A few miscellaneous fixes I found during usage:

• Updated readme to use the actual names I ended up going with in #1
• Fix bug when passing Pair object with on
• Fix bug in method definition for quantile_windows
• Test various keyword arguments for interval_join

[codecov[bot]]

Codecov Report

Merging #7 (98649d4) into main (394a7c1) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main       #7   +/-   ##
=======================================
  Coverage   89.50%   89.50%           
=======================================
  Files           1        1           
  Lines         162      162           
=======================================
  Hits          145      145           
  Misses         17       17           

Impacted Files	Coverage Δ
src/DataFrameIntervals.jl	89.50% <100.00%> (ø)

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