Update to selenium-assistant 0.3.0 to make tests work with Firefox

Author: marco-c

package.json

@@ -54,7 +54,7 @@
     "mocha": "^2.4.5",
     "portfinder": "^1.0.2",
     "request": "^2.69.0",
-    "selenium-assistant": "0.2.0",
+    "selenium-assistant": "0.3.0",
     "selenium-webdriver": "~2.53.2",
     "semver": "^5.1.0",
     "temp": "^0.8.3",