0.10 prerelease with webpack 2 increases bundle size

Created by: gavinwahl

On a newly created empty project and react-scripts@0.9.5, I get these bundle sizes for the production build after running yarn run build:

  46.12 KB  build/static/js/main.fcaea709.js
  289 B     build/static/css/main.9a0fe4f1.css

After upgrading to the 0.10.0 alpha (328cb32e), I get:

  46.28 KB (+163 B)  build/static/js/main.f27b292b.js
  317 B (+28 B)      build/static/css/main.1f6b6bee.css

I expect the bundle size not to increase after upgrading. In my production project, I get an even larger increase:

  268.18 KB (+2.22 KB)  build/static/js/main.1d20828f.js
  32.15 KB (+4.9 KB)    build/static/css/main.0d46d1be.css