Use hiredis parser if available

Explicit is better than implicit, but I don't think passing something like 'use_hiredis' or have subclasses like HiredisMonitorProtocol, HiredisSubscriberProtocol is a good idea.
So I made like it's done in redis-py: If hiredis available, use it.

[little benchmark](https://gist.github.com/etataurov/88b0efb495584bead0c6) shows expected result:
with hiredis:
```
done set-get: 0.0006s.
done lrange: 0.0019s.
```
without:
```
done set-get: 0.0006s.
done lrange: 0.0396s.
```