Simplified jest config and removed unneeded packages

config/jest/cssTransform.js

@@ -1,13 +0,0 @@
-
-// This is a custom Jest transformer turning style imports into empty objects.
-// http://facebook.github.io/jest/docs/en/webpack.html
-
-module.exports = {
-  process() {
-    return 'module.exports = {};';
-  },
-  getCacheKey() {
-    // The output is always the same.
-    return 'cssTransform';
-  },
-};