chore(package): update semantic-release to version 15.0.0

Closes #27

Author: greenkeeper[bot]

package.json

@@ -61,7 +61,7 @@
     "mocha": "3.4.2",
     "nodemon": "1.11.0",
     "nyc": "10.3.2",
-    "semantic-release": "6.3.6",
+    "semantic-release": "15.0.0",
     "serve-favicon": "2.4.3",
     "sinon": "2.3.5",
     "sinon-chai": "2.11.0",