chore(package): update phantomjs-prebuilt to version 2.1.15

Author: greenkeeper[bot]

package.json

@@ -42,7 +42,7 @@
     "karma-sourcemap-loader": "0.3.7",
     "karma-webpack": "2.0.4",
     "mocha": "3.5.0",
-    "phantomjs-prebuilt": "2.1.14",
+    "phantomjs-prebuilt": "2.1.15",
     "semver": "5.4.1",
     "should": "11.2.1",
     "ts-loader": "2.3.2",