Refactor Environments component in demo (#386)
Refactor Environments component in demo (#386)

This refactors the Environments component to do the following:

* Use a functional component rather than state (the state of the Environments component is already stored in the top-level app, so it should be passed down as a prop rather than being duplicated).
* Avoid local mutations when building columns
* Make the number of columns easy to change if necessary
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