Sentry 3.0 (WIP) [Do Not Merge Yet]

## Notable Changes

- [x] Allow for custom hashing strategies
- [x] Refactor permissions out into a driver-based system
- [ ] Refactor `*Provider` and `*Interface` implementations into single `*Repository` classes, stripping methods and simplifying where possible.
- [ ] Multiple sessions
- [ ] Multiple login columns
- [ ] Inter-account throttling and improved DDoS protection
- [ ] Improved integration with Laravel (`Sentry::basic()`, easy email integration with queues).
- [ ] Improved speed - make use of eager loading and caching.
- [ ] Allow use of implementations (such as Eloquent and Kohana ORM) to take place on the ORM level, without bloating Sentry with abstractions never used by Sentry.