Fix transform #1

I don’t know what exactly was wrong, whether browserify API has changed or whatever, but transform on browserify >6.3.3 works that way. This fixes https://github.com/mantoni/brout.js/issues/1 as well as https://github.com/mantoni/mochify.js/issues/54
Merge pull request #2 from dfcreative/patch-1

Fix transform #1