Upgrade to 0.3.x of es6-module-transpiler.

Note that 0.3.2 seems to have a bug with globals, in which it cannot build 
without at least one import named on the command line.  A nonsense import,
which is not actually used in the source, does not affect the output.

It is perfectly fine to remove `imports: {"__nothing" => "__nothing"}` for a 
version of the es6-module-transpiler that does not suffer from this problem.

cc @machty