In training notebook, save once per family instead of per reaction

[mliu49]

Now that saveTrainingReactions supports lists for metadata, this approach is much faster.

[codecov]

Codecov Report

Merging #1622 into master will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1622      +/-   ##
==========================================
- Coverage    41.5%   41.48%   -0.02%     
==========================================
  Files         176      176              
  Lines       29306    29306              
  Branches     6033     6033              
==========================================
- Hits        12163    12158       -5     
- Misses      16292    16296       +4     
- Partials      851      852       +1

Impacted Files	Coverage Δ
rmgpy/data/kinetics/family.py	52.67% <0%> (-0.24%)	⬇️

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[jimchu10]

Same as the script successfully finished the task