docs(deisctl): add unit search paths behavior to README
Merge pull request #1941 from mboersma/deisctl99-doc-search-paths

docs(deisctl): add unit search paths behavior to README
fix(deisctl): install only deisctl

./... means "this and all subpackages", but we only want to build
`deisctl`. The other problem seems to be that ./... doesn't actually
drop the main binary in the root.
Merge pull request #1950 from bacongobbler/build-deisctl

fix(deisctl): install only deisctl
refactor(makefile): cleanup and add release, dev-release target
refactor(tests): cleanup tests, move common logic into test-setup.sh