added deep clone returned state global setting

[roll314]

Hi Dan!
First of all - thank you for the coolest lib.
I seen #92 some time ago and i need that feature as well.
Could you please consider my PR?
Not sure i properly understand your vision of setting hierarhy.
I think as follow:

• global settings has some defaults;
• user could redefine part of global settings;
• user could pass specific settings (subset of global settings) for each store instance via construstor; in that case instance settings has a higher priority rather than global settings.

In original code global settings has the last word and nailed to the table - cannot be changed via constructor of store instance.

[DanWahlin]

Thanks for submitting this @roll314 and I apologize for taking so long to look at it. I've been ridiculously busy with my new position at Microsoft but as soon as I can come up for air and devote some time to this I will.