Getting a THREE is not defined error

Just installed this now. I'm using webpack to packaged everything up.

I've got the following setup at the top of my file

```js
var THREE = require('three');
var buffer = require('three-buffer-vertex-data');
```

I'm getting a THREE is not defined error from [line 62](https://github.com/Jam3/three-buffer-vertex-data/blob/master/index.js#L62) of `three-buffer-vertex-data`. Any ideas why i might be getting this error?

Cheers.