add documentation for wait-all tutorial
add documentation for wait-all tutorial

cgvarela/circuit,lgscofield/circuit,mzdravkov/circuit,bzz/circuit,mzdravkov/circuit,bzz/circuit,mjolk/circuit,tonestuff/circuit,ebookbug/circuit,beni55/circuit,tonestuff/circuit,bzz/circuit,rranshous/circuit,ebookbug/circuit,cgvarela/circuit,mjolk/circuit,rranshous/circuit,tonestuff/circuit,lgscofield/circuit,rranshous/circuit,lgscofield/circuit,ebookbug/circuit,beni55/circuit,bzz/circuit,mjolk/circuit,cgvarela/circuit,lgscofield/circuit,mzdravkov/circuit,cgvarela/circuit,mjolk/circuit,rranshous/circuit,ebookbug/circuit,tonestuff/circuit,mzdravkov/circuit,beni55/circuit,beni55/circuit