Upgrade to es6-module-transpiler@0.9

This upgrades to using `es6-module-transpiler@0.9` which contains the following changes:

- Add support for namespace imports (e.g. `import * as foo from 'foo'`).
- Fixed internal helper `mkdirpSync` that could cause `Container#write` to fail on some machines.
- Fixed bundle formatter renaming of function or class declarations in export default. Previously they were not properly renamed to prevent collision with other modules.
- Fixed bundle formatter rewriting identifiers inside named function expressions if the identifier shared a name with a module-scope binding.
- Simplify the CommonJS formatter output to use ES3.
- Use a common base class for all built-in formatters.
- Various internal cleanups.

— https://github.com/esnext/es6-module-transpiler/blob/master/CHANGELOG.md