translate README for ja_JP

translate README.md for ja_JP.

btw, how can I explain `* Great 'out of the box' feature set.` in `Features` of README? 
I tried to translate it, and I think that **out of the box** may means  *(idiomatic, of a product) Immediate(ly), without intervention from the customer. This software has to work out of the box, without any fancy installation.* 
and translate like this. 

if I mistake the meaning of this word, please let me know :)