running babel on node_modules
Hi,

I am working on a `react-sketchapp` project that uses skpm.  One of the node modules I am using has ES.next syntax that isn't getting recognized during compilation (`skpm build --watch --run`):
[the equals sign after `static propTypes`](https://gist.github.com/pcooney10/e2e699549e47284f3eae8aca390c2148#file-index-js-L18).

I have included a .babelrc file at the root of my project with the following settings, per suggestions from [here](https://stackoverflow.com/questions/35345000/equal-sign-in-bad-place-causes-unknown-token-exception) & [here](https://stackoverflow.com/questions/45177215/babel-webpack-settings-for-react-sketchapp-project-with-es2015-es-next): 

    {
      "presets": ["es2015", "react", "stage-0"],
      "plugins": ["transform-runtime", "transform-class-properties"]
    }

Does `skpm` ignore the `node_modules` folder? If so, how can I change that? A full repo where the issue can be reproduced is available [here](https://github.com/pcooney10/rn-calendar).