[WIP] Added support for validating the password against a blacklist

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | yes
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | No
| Fixed tickets | 
| License       | MIT

Todo

- [ ] Add tests
- [ ] Update README.md
- [ ] Provide a script for creating/updating a blacklist DB using the 500 worst passwords and such (http://www.skullsecurity.org/wiki/index.php/Passwords)