chore(package): update semantic-release to version 15.1.6

Closes #229

Author: greenkeeper[bot]

package.json

@@ -38,7 +38,7 @@
     "babel-preset-es2015-node5": "^1.1.2",
     "eslint": "^4.1.0",
     "mocha": "^4.0.1",
-    "semantic-release": "^11.0.2",
+    "semantic-release": "^15.1.6",
     "sequelize-cli": "^3.0.0",
     "supertest": "^3.0.0",
     "should": "^13.0.0"