Dogfood FB products in FB products.
Dogfood FB products in FB products.

Summary:
Update tutorial docs to use `yarn`.
Closes https://github.com/facebook/relay/pull/2184

Reviewed By: JenniferWang

Differential Revision: D6297783

Pulled By: kassens

fbshipit-source-id: a6cd38e019315c876d8ca811f9584e0499f87dcc

facebook/relay,zpao/relay,wincent/relay,xuorig/relay,dbslone/relay,freiksenet/relay,voideanvalue/relay,benjaminogles/relay,kassens/relay,josephsavona/relay,kassens/relay,apalm/relay,wincent/relay,kassens/relay,atxwebs/relay,josephsavona/relay,zpao/relay,apalm/relay,yungsters/relay,freiksenet/relay,kassens/relay,facebook/relay,wincent/relay,kassens/relay,atxwebs/relay,wincent/relay,wincent/relay,iamchenxin/relay,iamchenxin/relay,atxwebs/relay,iamchenxin/relay,xuorig/relay,zpao/relay,kassens/relay,apalm/relay,facebook/relay,xuorig/relay,voideanvalue/relay,yungsters/relay,voideanvalue/relay,freiksenet/relay,cpojer/relay,yungsters/relay,xuorig/relay,cpojer/relay,josephsavona/relay,atxwebs/relay,wincent/relay,cpojer/relay,facebook/relay,voideanvalue/relay,dbslone/relay,benjaminogles/relay,facebook/relay,voideanvalue/relay,xuorig/relay,xuorig/relay,benjaminogles/relay,cpojer/relay,iamchenxin/relay,facebook/relay,voideanvalue/relay