Add more comments to Jest, and bump version to 18.1.0
Add more comments to Jest, and bump version to 18.1.0

YousefED/DefinitelyTyped,jimthedev/DefinitelyTyped,georgemarshall/DefinitelyTyped,abbasmhd/DefinitelyTyped,zuzusik/DefinitelyTyped,alexdresko/DefinitelyTyped,mcrawshaw/DefinitelyTyped,AgentME/DefinitelyTyped,arusakov/DefinitelyTyped,minodisk/DefinitelyTyped,johan-gorter/DefinitelyTyped,smrq/DefinitelyTyped,micurs/DefinitelyTyped,dsebastien/DefinitelyTyped,benishouga/DefinitelyTyped,zuzusik/DefinitelyTyped,rolandzwaga/DefinitelyTyped,AbraaoAlves/DefinitelyTyped,alexdresko/DefinitelyTyped,georgemarshall/DefinitelyTyped,AbraaoAlves/DefinitelyTyped,benishouga/DefinitelyTyped,GiedriusGrabauskas/DefinitelyTyped,arusakov/DefinitelyTyped,isman-usoh/DefinitelyTyped,georgemarshall/DefinitelyTyped,johan-gorter/DefinitelyTyped,nycdotnet/DefinitelyTyped,one-pieces/DefinitelyTyped,chrootsu/DefinitelyTyped,ashwinr/DefinitelyTyped,zuzusik/DefinitelyTyped,AgentME/DefinitelyTyped,georgemarshall/DefinitelyTyped,smrq/DefinitelyTyped,benliddicott/DefinitelyTyped,aciccarello/DefinitelyTyped,laurentiustamate94/DefinitelyTyped,borisyankov/DefinitelyTyped,arusakov/DefinitelyTyped,magny/DefinitelyTyped,rolandzwaga/DefinitelyTyped,AgentME/DefinitelyTyped,ashwinr/DefinitelyTyped,progre/DefinitelyTyped,QuatroCode/DefinitelyTyped,aciccarello/DefinitelyTyped,nycdotnet/DefinitelyTyped,dsebastien/DefinitelyTyped,abbasmhd/DefinitelyTyped,AgentME/DefinitelyTyped,GiedriusGrabauskas/DefinitelyTyped,YousefED/DefinitelyTyped,chrootsu/DefinitelyTyped,amir-arad/DefinitelyTyped,progre/DefinitelyTyped,jimthedev/DefinitelyTyped,markogresak/DefinitelyTyped,isman-usoh/DefinitelyTyped,aciccarello/DefinitelyTyped,AbraaoAlves/DefinitelyTyped,jimthedev/DefinitelyTyped,minodisk/DefinitelyTyped,borisyankov/DefinitelyTyped,QuatroCode/DefinitelyTyped,mcrawshaw/DefinitelyTyped,magny/DefinitelyTyped,mcliment/DefinitelyTyped,benishouga/DefinitelyTyped