Add karma based testing

karma.conf.js

@@ -0,0 +1,29 @@
+var webpackConfig = require('./webpack.config.js');
+
+// Karma configuration
+module.exports = function(config) {
+  config.set({
+		browsers: [ 'Chrome' ], //run in Chrome
+		frameworks: [ 'mocha' ], //use the mocha test framework
+    // ... normal karma configuration
+    files: [
+      // all files ending in "_test"
+      {pattern: 'test/*_test.js', watched: false},
+      {pattern: 'test/**/*_test.js', watched: false}
+      // each file acts as entry point for the webpack configuration
+    ],
+
+    preprocessors: {
+      // add webpack as preprocessor
+      'test/*_test.js': ['webpack'],
+      'test/**/*_test.js': ['webpack']
+    },
+
+    webpack: webpackConfig,
+    webpackMiddleware: {
+      // webpack-dev-middleware configuration
+      // i. e.
+      stats: 'errors-only'
+    }
+  });
+};