Fix hdf5 bug with new cgm options

[gbrammer]

Fix for #52.

[codecov]

Codecov Report

Attention: Patch coverage is 74.07407% with 7 lines in your changes missing coverage. Please review.

Project coverage is 62.67%. Comparing base (078bada) to head (f22d4cc).
Report is 4 commits behind head on master.

Files with missing lines	Patch %	Lines
eazy/hdf5.py	50.00%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #53      +/-   ##
==========================================
+ Coverage   61.56%   62.67%   +1.11%     
==========================================
  Files          14       14              
  Lines        5354     5375      +21     
==========================================
+ Hits         3296     3369      +73     
+ Misses       2058     2006      -52     

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