bugfix #2568 transforms commonjs modules to ES2015

[eusorov]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Bugfix some browsers not showing gekko UI (IE 10, OPERA mini Android) #2568

• What is the current behavior? (You can also link to an open issue here)
  see some browsers not showing gekko UI (IE 10, OPERA mini Android) #2568

• What is the new behavior (if this is a feature change)?
  commonjs modules get transpiled with babel.

• Other information:

[askmike]

This works great! Thanks a lot. I will update my stackoverflow question with your answer.

EDIT: @eusorov this works but I'm not sure why. As the plugin you added does:

This plugin transforms ES2015 modules to CommonJS.

While the reduceState function is written in CommonJS. This PR worked in my tests, but I'm not understanding why.