Add simple jest test suite for hugla constructor

package.json

@@ -39,7 +39,7 @@
     "compile": "babel --presets es2015,es2016 -d lib/ src/",
     "prepublish": "npm run compile",
     "lint": "./node_modules/.bin/eslint --ext .js src",
-    "test": "",
-    "test-ci": ""
+    "test": "./node_modules/.bin/jest",
+    "test-ci": "./node_modules/.bin/jest --coverage"
   }
 }

test/hugla.spec.js

@@ -0,0 +1,7 @@
+const Hugla = require('./../lib/hugla.js');
+
+test('new Hugla() should throw an Error if appDir is not provided', () => {
+  expect(() => {
+    new Hugla();
+  }).toThrow(Error);
+});