Error while building ./my-command.js. You may need the appropriate loader to handle this file type
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_I am..._

| -------------------------------------------------------------------------------------------------
| Reporting a bug or issue
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**Expected behavior:**
Should be able to use ES6+/ES7 features with the appropriate `.babelrc` configuration.

**Observed behavior:**
Error while building from an npm module that uses the following ES6+/ES7 syntax:

    static propTypes = {
      theme: PropTypes.object,
      markedDates: PropTypes.object,
      ...
    };

**How to reproduce:**
 With [this repo](https://github.com/pcooney10/rn-calendar). The presets in my .babelrc file are `["react", "stage-0", "es2015"]`. I have also tried the following plugins: `["transform-object-rest-spread", "transform-class-properties"]`.

**Sketch version:**
43.1

**Please attach screenshots, a zip file of your project, and/or a link to your github project**
**Repo**: https://github.com/pcooney10/rn-calendar
![image](https://user-images.githubusercontent.com/11021913/28342458-7be75a5c-6be6-11e7-9369-bf1c9df0615c.png)

