Modified Scale() to return input if units not same type

[nolanmar511]

Fixes #153

[codecov-io]

Codecov Report

Merging #159 into master will increase coverage by 0.14%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #159      +/-   ##
==========================================
+ Coverage    53.1%   53.24%   +0.14%     
==========================================
  Files          32       32              
  Lines        6096     6098       +2     
==========================================
+ Hits         3237     3247      +10     
+ Misses       2508     2501       -7     
+ Partials      351      350       -1

Impacted Files	Coverage Δ
internal/measurement/measurement.go	30.19% <100%> (+4.69%)	⬆️

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