DOC: Add basic Neuroscout Documentation

[adelavega]

Closes #253

Documentation will be served here: https://neuroscout.github.io/neuroscout/

To edit docs, edit files in docs/ then run: mkdocs serve. This starts a local server to edit the docs.

Finally, to server, usec ommand mkdocs gh-deploy. This will automatically update the gh-pages branch, which will push live changes to the docs.

[codecov-io]

Codecov Report

Merging #685 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #685   +/-   ##
=======================================
  Coverage   85.67%   85.67%           
=======================================
  Files          66       66           
  Lines        2932     2932           
=======================================
  Hits         2512     2512           
  Misses        420      420

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[adelavega]

@tyarkoni I added some basic docs for "Browsing" and the cli. It's live so you can check it out.