Upgrade PG to latest version

See #25

Author: c-w

package.json

@@ -18,7 +18,7 @@
     "http-status-codes": "^1.0.5",
     "morgan": "^1.6.1",
     "node-fetch": "^1.3.3",
-    "pg": "^6.1.2",
+    "pg": "^7.4.1",
     "request": "^2.79.0",
     "service-utils": "^1.0.31",
     "through2": "^2.0.3",