Add time logging in eval_metric.py

[zhiqwang]

Adding time logging in eval_metric.py to make the printing look better.

[codecov]

Codecov Report

Merging #150 (b2a14f1) into master (db7e7dd) will not change coverage.
The diff coverage is n/a.

❗ Current head b2a14f1 differs from pull request most recent head c4b9bf2. Consider uploading reports for the commit c4b9bf2 to get more accurate results

@@           Coverage Diff           @@
##           master     #150   +/-   ##
=======================================
  Coverage   84.50%   84.50%           
=======================================
  Files          12       12           
  Lines         813      813           
=======================================
  Hits          687      687           
  Misses        126      126           

Flag	Coverage Δ
unittests	84.50% <ø> (ø)

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