[WIP] Concatenation Sourcemaps

This enables real sourcemaps for both app and vendor. It's pretty fast. Please give it a whirl and help me work out the kinks.

 - [ ] switch broccoli-es6modules from multiGlob to funnel
 - [ ] add inline dataURI sourcemap reader to fast-sourcemap-concat
 - [ ] try enabling upstream sourcemap generation for esnext, coffee, etc.