Craft custom messages based on linter feedback; misc

* Combine duplicated linting messages
* Add messages of appropriate level to configured linter feedback
* Properly handle values we can't get via code execution
* Improve layout function so doesn't break lists
* Fix duplicate message in sorting advisor
* Fix layout of lists in comments
* Add documentation about need for raw strings as demo inputs to ast.parse (new line problem)
* Remove nose from requirements
* Bump version
2 jobs for master
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