Don't let BROWSER env variable clobber globals in Webpack builds.
Don't let BROWSER env variable clobber globals in Webpack builds.

Fixes #32. Cheers to @iam4x.

dmitrif/isomorphic500,veeracs/isomorphic500,jxnblk/isomorphic500,devypt/isomorphic500,jmfurlott/isomorphic500,pheadra/isomorphic500,jeffhandley/oredev-sessions,beeva-davidgarcia/isomorphic500,fustic/isomorphic500,elfinxx/isomorphic500,gpbl/isomorphic500,ryankanno/isomorphic500,saitodisse/isomorphic500,jonathanconway/MovieBrowser,w01fgang/isomorphic500