[Docs] Supported value types.

[mktums]

I suggest to provide some info in README or wherever you might think it should be about supported value types and their cast logic for both Redis and Database backends with screenshots of admin site.

For example:
I need to store/retrieve/edit tuple of strings in certain key, but how it will looks like in admin site? as value, value,… or (u'value', u'value',…)?

Thanks in advance for your reply.

[jezdez]

Closing in favor of #48.