Bower and handling of external dependencies

I think it's worth discussing how `es6-module-loader` should handle the esprima dependency when installed via a package manager. Since `esprima` is loaded lazily and the loader expects it in a certain place, it should be included in the package. Vendoring external dependencies, however, is nonoptimal when using package managers.

I attached a sample `bower.json` that excludes the bundled esprima version and lists it as dependency. How would you like to handle this?