Fixing normalization in dataloader

[zhiqwang]

Fixing #60

[codecov]

Codecov Report

Merging #124 (a7ebfdf) into master (e52771e) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #124   +/-   ##
=======================================
  Coverage   83.54%   83.54%           
=======================================
  Files           8        8           
  Lines         784      784           
=======================================
  Hits          655      655           
  Misses        129      129           

Flag	Coverage Δ
unittests	83.54% <ø> (ø)

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