Make sure we actually build netlify-cms as library (#169)

* Build netlify-cms as a library

* Bump version

webpack.dev.js

@@ -20,6 +20,9 @@ module.exports = merge.smart(require('./webpack.base.js'), {
     path: path.join(__dirname, 'dist'),
     filename: '[name].js',
     publicPath: `http://${ HOST }:${ PORT }/`,
+    library: 'netlify-cms',
+    libraryTarget: 'umd',
+    umdNamedDefine: true,
   },
   context: path.join(__dirname, 'src'),
   module: {