remove spurious require on DataFrames

[KristofferC]

No description provided.

[codecov-io]

Codecov Report

Merging #91 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master     #91   +/-   ##
======================================
  Coverage    71.4%   71.4%           
======================================
  Files           9       9           
  Lines         619     619           
======================================
  Hits          442     442           
  Misses        177     177

Impacted Files	Coverage Δ
src/numeric.jl	0% <ø> (ø)	⬆️

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