Add n_subjects to upload options

[adelavega]

Add n_subjects as this is required meta-data for NeuroVault.

[codecov-io]

Codecov Report

Merging #37 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #37   +/-   ##
=======================================
  Coverage   93.95%   93.95%           
=======================================
  Files          16       16           
  Lines         430      430           
=======================================
  Hits          404      404           
  Misses         26       26

Impacted Files	Coverage Δ
tests/test_analysis.py	100% <ø> (ø)	⬆️
setup.py	0% <ø> (ø)	⬆️
pyns/models/analysis.py	87.5% <100%> (ø)	⬆️

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