add docstored field retreival

Hi, John

this is hao. Long time no see. How are you doing?

I saw this clue tool, which is pretty cool. Thanks for the awesome tool.

I added two functions : 
1) for search: java -jar clue.jar search displayStored query
where "displayStored" means to display stored value

2) to dislay stored values for a given docId
java -jar clue.jar docstored docId

This is useful for many debug cases. Please review and pull! 

And Congratulations for twitter IPO! 
thanks! 

hao