Reintroduce parallelism to avoid Travis timeouts

- Split suites by services/non_services
- Split suites by transactional/non_transactional
- Separate api specs and rubocop from the rest

Signed-off-by: James Myers <jmyers@pivotallabs.com>
Consolidate rubocop and api specs

To free up a Travis worker sooner [#71446796]

Signed-off-by: James Myers <jmyers@pivotallabs.com>
Explain why we use non_transactional isolation in service_broker_spec

Signed-off-by: James Myers <jmyers@pivotallabs.com>
Remove unused argument

Signed-off-by: James Myers <jmyers@pivotallabs.com>