fix ranges of Measurements without stop argument

[simeonschaub]

supersedes #55

[codecov-io]

Codecov Report

Merging #56 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #56      +/-   ##
==========================================
+ Coverage   96.32%   96.33%   +<.01%     
==========================================
  Files          12       12              
  Lines         544      545       +1     
==========================================
+ Hits          524      525       +1     
  Misses         20       20

Impacted Files	Coverage Δ
src/conversions.jl	87.5% <100%> (+0.83%)	⬆️

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[giordano]

Thanks!