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Fixes #2022
Merge pull request #2058 from jalyna/show-comments-on-iteration

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Add nits_receieved page

* Add acceptance tests for nits
* Link to nits receieved & given from nitstats page, not account page
* Standardize API endpoints:
  /nits/:username/stats
  /nits/:username/given
  /nits/:username/received
* Move ActiveRecord scopes from Routes to Comment model.
* For nits given, say: "Given to #{nitpick.submission.user}"
* For nits received, say: "Receieved from #{nitpick.user}"
Move nits routes and views into own section
Add date submitted of each iteration on user profile. Closes #1958