This improves incremental build time when working on what was previously
the root package. For example, previously all plugins would be rebuilt
with a change to `src/commands/classified/external.rs`, but now only
`nu-cli` will have to be rebuilt (and anything that depends on it).
* start playing with ways to use the uniq command
* WIP
* Got uniq working, but still need to figure out args issue and add tests
* Add some tests for uniq
* fmt
* remove commented out code
* Add documentation and some additional tests showing uniq values and rows. Also removed args TODO
* add changes that didn't get committed
* whoops, I didn't save the docs correctly...
* fmt
* Add a test for uniq with nested json
* Add another test
* Fix unique-ness when json keys are out of order and make the test json more complicated
