Documentation/configuration.md: Fix typo.
Documentation/configuration.md: Fix typo.

boostrapping -> bootstrapping

a-robinson/etcd,hongchaodeng/etcd,raoofm/etcd,HideoYamauchi/etcd,mkumatag/etcd,heyitsanthony/etcd,akauppi/etcd,glycerine/etcd,bluebreezecf/etcd,bluebreezecf/etcd,etcd-io/etcd,handsomesun/etcd,coreos/etcd,chipironcin/etcd,ravigadde/etcd,etcd-io/etcd,swingbach/etcd,ravigadde/etcd,tamird/etcd,dannysauer/etcd,yudai/etcd,a-robinson/etcd,mkumatag/etcd,coreos/etcd,swingbach/etcd,luxas/etcd,zaphod-concur/etcd,oscarrr110/etcd,dnaeon/etcd,plasticbox/etcd,joshix/etcd,whuwxl/etcd,rnaveiras/etcd,ajityagaty/etcd,visheshnp/etcd,sebrandon1/etcd,li-ang/etcd,handsomesun/etcd,fasaxc/etcd,jonboulle/etcd,rchicoli/etcd,nekto0n/etcd,fanminshi/etcd,kkaneda/etcd,siddontang/etcd,achanda/etcd,ajityagaty/etcd,purpleidea/etcd,CrazyJvm/etcd,wowsoso/etcd,bdarnell/etcd,purpleidea/etcd,ktateish/etcd,siddontang/etcd,shawnps/etcd,sayden/etcd,plasticbox/etcd,raoofm/etcd,endocode/etcd,glycerine/etcd,mickep76/etcd,lorneli/etcd,cchamplin/etcd,ktateish/etcd,gyuho/etcd,tamird/etcd,xychu/etcd,YuleiXiao/etcd,vimalk78/etcd,whuwxl/etcd,kkaneda/etcd,wantonsolutions/dinv-etcd,fasaxc/etcd,armstrongli/etcd,qqsun8819/etcd,Timer/etcd,yudai/etcd,bdarnell/etcd,qqsun8819/etcd,jonboulle/etcd,mqliang/etcd,jlamillan/etcd,westhood/etcd,gyuho/etcd,StorReduce/etcd,cockroachdb/etcd,insequent/etcd,achanda/etcd,luxas/etcd,heyitsanthony/etcd,rnaveiras/etcd,xiang90/etcd,improbable-io/etcd,dannysauer/etcd,westhood/etcd,dnaeon/etcd,mqliang/etcd,fanminshi/etcd,wantonsolutions/dinv-etcd,Timer/etcd,xychu/etcd,mickep76/etcd,joshix/etcd,rnaveiras/etcd,tguangch/etcd,visheshnp/etcd,mkumatag/etcd,sebrandon1/etcd,li-ang/etcd,sinsharat/etcd,tguangch/etcd,lumjjb/etcd,cockroachdb/etcd,linuxcer/etcd,etcd-io/etcd,jlamillan/etcd,endocode/etcd,OyTao/etcd_learning,glevand/coreos--etcd,hongchaodeng/etcd,oscarrr110/etcd,insequent/etcd,zaphod-concur/etcd,mqliang/etcd,nekto0n/etcd,akauppi/etcd,chipironcin/etcd,ajityagaty/etcd,armstrongli/etcd,HideoYamauchi/etcd,sofuture/etcd,CrazyJvm/etcd,sofuture/etcd,YuleiXiao/etcd,cchamplin/etcd,sayden/etcd,linuxcer/etcd,lumjjb/etcd,wowsoso/etcd,sinsharat/etcd,shawnps/etcd,xiang90/etcd,glevand/coreos--etcd,vimalk78/etcd,rchicoli/etcd,fasaxc/etcd,wantonsolutions/dinv-etcd,StorReduce/etcd,OyTao/etcd_learning,improbable-io/etcd,lorneli/etcd