Enforce v0.3.2 of module transpiler.

es6-module-transpiler 0.3.2 does not produce output compatible with 0.2.x 
consumers because it now supports mixing named & default exports.

For 0aa5998715657f452a047f1c357c614ebe01b09b and later users will need to
`var Router = requireModule("Router")['default']` rather  than the 0.2.x style
`requireModule("Router")`.  Users using es6-module-transpiler simply need to 
upgrade their transpiler.

- see https://github.com/square/es6-module-transpiler#default-exports-1