Not compatible with lodash 4.17

Geppetto cannot be used with lodash 4.17.
Since lodash dropped support for binding this to their functions

```
         _.each(wiring.values, function(value, key) {
                this.wireValue(key, value);
            }, this)
```

should be

```
_.each(wiring.values, (value, key) => {
          this.wireValue(key, value);
});
```