check concept, decorators, fixes, modifications

- added check_subprocess function to allow multiple runs and assertions
of external program calls from same test case
- added concept of checks in addition to tests and suites, calculated
and displayed in results
- added decorators for test case header, name, and description
- corrected setup teardown defined as suite function to only take place
at start and end of suite not each test case
- small modifications to run_subprocess
- added argument to nbstream_readerwriter.py for whether to print
stream as it is fed into the queue
- various tweaks, fixes