Add compose override example

[g-k]

Changes:

• add an example docker compose override file for local dev
• add a unit-test make target (the image is only used for CI, but it's included since we have make integration-test)
• readme: remove local install directions
  • go get is deprecated
  • local dev requirements are outdated and unsupported due to signers shelling out and writing stuff to temp now
• readme: add docker-compose install / local dev directions

[coveralls]

Pull Request Test Coverage Report for Build 7633

• 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 71.27%

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Totals
Change from base Build 7628:	0.0%
Covered Lines:	3401
Relevant Lines:	4772

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💛 - Coveralls