change to cached_responses; actively prune table

migrations/010-cached-requests.js

@@ -3,13 +3,14 @@
 var db = require('./db')
 
 exports.up = function (next) {
-  db.query('CREATE TABLE IF NOT EXISTS cached_requests ( ' +
+  db.query('CREATE TABLE IF NOT EXISTS cached_responses ( ' +
     'id serial PRIMARY KEY, ' +
     'device_fingerprint text NOT NULL, ' +
     'session_id uuid NOT NULL, ' +
     'path text NOT NULL, ' +
     'method text NOT NULL, ' +
     'body json NOT NULL, ' +
+    'created timestampz NOT NULL DEFAULT now(), ' +
     'UNIQUE (device_fingerprint, session_id, path, method) ' +
     ')', next)
 }