BF: consistent yaml (default_flow_style=False)

[yarikoptic]

Info : yaml/pyyaml#256

Closes #58

[codecov]

Codecov Report

Merging #59 into master will increase coverage by 0.05%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #59      +/-   ##
==========================================
+ Coverage   55.93%   55.99%   +0.05%     
==========================================
  Files          32       32              
  Lines        2517     2520       +3     
==========================================
+ Hits         1408     1411       +3     
  Misses       1109     1109

Flag	Coverage Δ
#unittests	55.99% <100%> (+0.05%)	⬆️

Impacted Files	Coverage Δ
dandi/download.py	0% <ø> (ø)	⬆️
dandi/utils.py	67.06% <100%> (+0.6%)	⬆️
dandi/dandiset.py	39.53% <100%> (ø)	⬆️

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