Add note in INSTALL regarding Docker installation

[caleb-johnson]

This note is at least useful for developers who will commonly have large .tox directories in their local repository, along with other caches which speed up local CI.

This could also be useful for someone running a local install and using the repository as a dumping grounds for results.

[coveralls]

Pull Request Test Coverage Report for Build 9308881765

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 9306464756:	0.0%
Covered Lines:	2401
Relevant Lines:	2401

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💛 - Coveralls

[garrison]

This note is at least useful for developers who will commonly have large .tox directories in their local repository, along with other caches which speed up local CI.

Are you seeing this with .tox specifically? .tox/ is listed in .dockerignore, but maybe we need to list **/.tox instead.

[garrison]

(I am not opposed to adding a note, but I do want to fix the problem to the extent possible that we can.)

[caleb-johnson]

No, you are right. This came up developing in another repo. We are covered here. Closing