Update dev install script

I'm getting this set up to bring the SecureDropDemo.org site up-to-date with recent changes.

Changes are:
- installing bcrypt and bcrypt-python
- installing from both requirements.txt files
- /tmp folder used in example_config.py
- moved bcrypt key generation before database table creation, because otherwise BCRYPT_ID_SALT == BCRYPT_GPG_SALT and ```import db``` fails