fix(package): update node-pg-migrate to version 3.5.1

Closes #27

Author: greenkeeper[bot]

package.json

@@ -14,7 +14,7 @@
     "convict": "^4.0.0",
     "express": "^4.15.3",
     "listify": "^1.0.0",
-    "node-pg-migrate": "^2.7.0",
+    "node-pg-migrate": "^3.5.1",
     "pg-connection-string": "^0.1.3",
     "pg-promise": "^5.6.2",
     "request-promise": "^4.2.1",