Fix self-signed certificate error when connecting to PG

As per brianc/node-postgres#2009

Author: em-cd

lib/PostgresDb.js

@@ -9,7 +9,9 @@ const pgp = require('pg-promise')({
 
 const PostgresDb = pgp({
   connectionString: process.env.DATABASE_URL,
-  ssl: true
+  ssl: {
+    rejectUnauthorized: false
+  }
 });
 
 module.exports = PostgresDb;