Use `install_requires` instead of `requires` in the package setup script
Major update to make it work with Haystack 2.0

- Haystack 2.0 uses a new mechanism for data updates: instead of being
  handled directly by the SearchIndex instance, there's a
  "SignalProcessor" that exists solely for the purpose of connecting
  Django signals to index updates [1].
- Now instead of providing a SearchIndex subclass, it's included a
  "signals" module with a "SignalProcessor" subclass called
  "RQueueSignalProcessor", which when used hooks up the registered
  model's save/delete signals with the configured RQ task queues. To
  use it, just include this in your Django project's settings module:

    HAYSTACK_SIGNAL_PROCESSOR = 'haystack_rqueue.signals.RQueueSignalProcessor'

- A example test project is included

[1] https://django-haystack.readthedocs.org/en/latest/signal_processors.html