Speed up webpack bundle builds
Speed up webpack bundle builds

This is the equivalent of:

https://github.com/facebook/relay/commit/f7f6c100b98450b9587a2bbf3fdaf21c78b024cc

Speeds up the first-build from 12s to 4s on my machine.

sogko/relay-starter-kit,iamchenxin/relay-starter-kit,relayjs/relay-starter-kit,roshane/relay-starter-kit-03012016,Troop18/mytroop.site,TribeMedia/relay-starter-kit,chenwei0104/starwars,stefanRitter/relay-tutorial,blendersfun/seattle-theatre-site2,stefanRitter/relay-tutorial,rblakeley/relay-example-players-positions,Troop18/mytroop.site,clairefritz/todo,blendersfun/seattle-theatre-site2,ranjithnori/lemons-list,yyankowski/relay-notes,18601673727/relay-starwar,chenwei0104/starwars,Aweary/relay-starter-kit,namelos/relay-starter-kit,relayjs/relay-starter-kit,namelos/relay-starter-kit,Electric-Lizard/find-coop,clairefritz/todo,sogko/relay-starter-kit,Troop18/mytroop.site,TribeMedia/relay-starter-kit,rblakeley/relay-example-players-positions,iamchenxin/relay-starter-kit,Aweary/relay-starter-kit,ranjithnori/lemons-list,roshane/relay-starter-kit-03012016,18601673727/relay-starwar,yyankowski/relay-notes,Electric-Lizard/find-coop