Fix compatability with Sprockets
Fix compatability with Sprockets

Broke as of https://github.com/rails/sprockets/commit/cdc8405577a59cbd704d99df25f437ab2b49e8c7

Signed-off-by: Jesse Stuart <a5c95b3d7cb4d0ae05a15c79c79ab458dc2c8f9e@jessestuart.ca>

jvatic/es6-module-mapper,jvatic/es6-module-mapper