replace old crawler, without specific crawler and saver implementation

app/crawler/savers/postgres.js

@@ -0,0 +1,28 @@
+class PostgresSaver {
+  constructor(url) {
+    this.url = url;
+  }
+
+  connect() {
+    //TODO: It seems we never worry about open/close connection with Sequelize ?
+    //TODO: Check if postgres is ready
+    return true;
+  }
+
+  async save(results) {
+    let resultsForMongo = Object.keys(results).map(key => {
+      return results[key];
+    });
+
+    for (const doc of resultsForMongo) {
+      this.collection.update({ url: doc.url }, doc, { upsert: true });
+    }
+  }
+
+  close() {
+    //TODO: It seems we never worry about open/close connection with Sequelize ?
+    return true;
+  }
+}
+
+module.exports = PostgresSaver;