Support for SCAN commands.

[ioga]

Implemented SCAN/SSCAN/HSCAN/ZSCAN commands support.

[ioga]

By the way, main python redis library has a useful scan_iter method, but I cannot think of a good way to implement it in twisted given that python iterators don't play well with deferreds.

I can suggest two options:

• implement scan_all method, which will return the list of all results, i.e. basically do the same as KEYS, but using a lot of SCAN commands.
• scan_map method, which will accept a callable argument and execute it for every key.

Thoughts?

[ioga]

Any comment on this?

[fiorix]

LGTM

[fiorix]

Thanks!