note that SPLASH_SLOT_POLICY value isn't a string

[iAnanich]

Put a little note about what value should SPLASH_SLOT_POLICY setting have.

I want this moment to be noted in README.rst because it's a little confusing at first, when you need to import something in settings.py while Scrapy needs only string paths to mentioned objects.
I think it would be better to refactor how plugin processes settings to import needed object itself, but not inside settings.py to keep Scrapy's style.

[kmike]

I think it would be better to refactor how plugin processes settings to import needed object itself, but not inside settings.py to keep Scrapy's style.

I'm fine with such change, as soon it is backwards compatible.

[kmike]

Thanks @iAnanich!