update README.md for test fixture
update README.md for test fixture

Co-authored-by: Connor Braa <e624947c8d30070ca3f5f65daa9bdf76de21947b@pivotal.io>
Co-authored-by: Tim Downey <ac5faf2072a7e8487ec8b27348636434d5c3410d@pivotal.io>

cloudfoundry-incubator/cc-uploader