concurrency: extend STM interface to Get from any of a list of keys
concurrency: extend STM interface to Get from any of a list of keys

Now possible to fetch multiple keys in a single txn.

ajityagaty/etcd,insequent/etcd,vimalk78/etcd,rnaveiras/etcd,mickep76/etcd,xiang90/etcd,plasticbox/etcd,heyitsanthony/etcd,etcd-io/etcd,sinsharat/etcd,gyuho/etcd,jlamillan/etcd,mkumatag/etcd,armstrongli/etcd,CrazyJvm/etcd,glevand/coreos--etcd,lorneli/etcd,sinsharat/etcd,mqliang/etcd,plasticbox/etcd,a-robinson/etcd,mkumatag/etcd,bdarnell/etcd,visheshnp/etcd,rnaveiras/etcd,bluebreezecf/etcd,sebrandon1/etcd,insequent/etcd,fanminshi/etcd,dannysauer/etcd,coreos/etcd,mqliang/etcd,yudai/etcd,li-ang/etcd,armstrongli/etcd,whuwxl/etcd,vimalk78/etcd,fanminshi/etcd,akauppi/etcd,rnaveiras/etcd,lumjjb/etcd,cockroachdb/etcd,handsomesun/etcd,dannysauer/etcd,bdarnell/etcd,etcd-io/etcd,visheshnp/etcd,sebrandon1/etcd,YuleiXiao/etcd,xiang90/etcd,bluebreezecf/etcd,handsomesun/etcd,mqliang/etcd,lorneli/etcd,heyitsanthony/etcd,tguangch/etcd,joshix/etcd,joshix/etcd,li-ang/etcd,yudai/etcd,ajityagaty/etcd,cockroachdb/etcd,YuleiXiao/etcd,lumjjb/etcd,ravigadde/etcd,mickep76/etcd,whuwxl/etcd,a-robinson/etcd,glevand/coreos--etcd,jlamillan/etcd,akauppi/etcd,ravigadde/etcd,tguangch/etcd,gyuho/etcd,ajityagaty/etcd,coreos/etcd,mkumatag/etcd,CrazyJvm/etcd,etcd-io/etcd