I want to embed one my specific chart in dahsboard of kibana. For that I need inject my JS into Kibana source. I have followed by instructions <https://github.com/elastic/kibana/blob/master/CONTRIBUTING.md> to provide test environment, but I have obtained an error after "./kibana --dev"

```
let _ = require('lodash');
^^^

node.js:201
          throw e; // process.nextTick error, or 'error' event on first tick
          ^
SyntaxError: Unexpected strict mode reserved word
at Module._compile (module.js:429:25)
at Object..js (module.js:459:10)
at Module.load (module.js:348:32)
at Function._load (module.js:308:12)
at Array.0 (module.js:479:10)
at EventEmitter._tickCallback (node.js:192:41)

```

Can anybody help me with start environment, or advice. Probably, I am moving by wrong way...my general goal (inject my JS code into Kibana) can be reached by another approach.

Thanks