Require tests to pass before subperseusing

Summary:
`make subperseus` or `make all` will now fail and not copy files to
webapp if any tests do not pass.

Also improves Makefile help slightly.

Test Plan:
 * `make subperseus` -> see tests ran
 * edit a test to fail and repeat -> see `make` didn't list files being
   copied

Auditors: charlie