Modified the Arkane ScanLog documentation

[alongd]

Added a short description of Angle and its units when a ScanLog is read from a text file.
Also corrected a minor typo in common.py

[amarkpayne]

Looks good! I'll merge this once the tests have passed.

[codecov]

Codecov Report

Merging #1650 into master will increase coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1650      +/-   ##
==========================================
+ Coverage    41.8%   41.82%   +0.01%     
==========================================
  Files         177      177              
  Lines       29455    29455              
  Branches     6059     6059              
==========================================
+ Hits        12314    12319       +5     
+ Misses      16271    16267       -4     
+ Partials      870      869       -1

Impacted Files	Coverage Δ
rmgpy/data/kinetics/family.py	52.9% <0%> (+0.23%)	⬆️

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