avoid: “warning: possible EventEmitter memory leak detected”
Merge pull request #850 from stefanpenner/avoid-event-emitter-warning

avoid: “warning: possible EventEmitter memory leak detected”
add es3-safe-transpile step

currently:

```js
promise.finally -> promise[‘finally’]
promise.catch   -> promise[‘catch’]
a.default       -> a[‘default’]
// and some more..
```

see: https://github.com/stefanpenner/es3-safe-recast for more