Run tests in real browsers with Karma

package.json

@@ -15,7 +15,8 @@
     "pretest": "eslint tasks test test_rendering src examples",
     "lint-package": "eslint --fix build/package",
     "test": "node tasks/test.js",
-    "debug-server": "node tasks/serve-lib.js"
+    "debug-server": "node tasks/serve-lib.js",
+    "karma": "node tasks/test-all.js start test/karma.config.js"
   },
   "main": "dist/ol.js",
   "repository": {
@@ -61,6 +62,10 @@
     "istanbul": "0.4.5",
     "jquery": "3.2.1",
     "jscodeshift": "^0.3.30",
+    "karma": "^1.7.0",
+    "karma-chrome-launcher": "^2.1.1",
+    "karma-mocha": "^1.3.0",
+    "karma-sauce-launcher": "^1.1.0",
     "marked": "0.3.6",
     "metalsmith": "2.3.0",
     "metalsmith-layouts": "1.8.1",