This variable was a temporary measure from https://github.com/scitran/core/pull/190 and never fully removed until now.

add new ENV required variable

- Entrypoint has new $PRE_RUNAS_CMD that allows running of root tasks before dropping privs.
- Added $SCITRAN_RUNTIME_PROTOCOL for explicit designation of http vs https.
- Updated README.md examples.
- No longer using requirements_dev.txt due to long install time.

- add two new variables to sample.config
- update defaults in config.py to be strings as that's how environment
  variables come in by default