increase post cache size

src/posts/cache.js

@@ -4,7 +4,7 @@ var LRU = require('lru-cache');
 var meta = require('../meta');
 
 var cache = LRU({
-	max: parseInt(meta.config.postCacheSize, 10) || 1048576,
+	max: parseInt(meta.config.postCacheSize, 10) || 5242880,
 	length: function (n) { return n.length; },
 	maxAge: 0,
 });