Configure using .indexrc.js

[ryardley]

Allow for configuration via configuration file. probably .indexrc.js or something similar

[ryardley]

Format:

module.exports = {
  indexes: [{
    exportAll: false,
    exportNamed: true,
    modules: '**/modules/',
    outputFilename: 'index.js',
    submodules: ['*/', '*.js'],
    submodulesIgnore: 'index.js',
  }]
}