examples of non-env based configuration

[jbarrus]

It would be nice to have some documentation of using babel without environment based configuration. For gulp users, for example, you might be using babel to do multiple things in a single run and env variables wouldn't make sense.

For example, when used with a the webpack babel loader, you can use the query param to configure babel options:

module: {
  preLoaders: [
    {
      test: /\.js$/, loader: 'babel', exclude: /node_modules/,
      query: {
        plugins: [
          ['istanbul', {
            'exclude': [
              '**/*.spec.js'
            ]
          }]
        ]
      }
    }
  ]
}

[bcoe]

@jbarrus would love some help adding this documentation to the README 👍

[bcoe]

this would be a great first contribution for anyone who's interested in updating docs.