some prep work to allow for checking of dependency versions. Also updated upgrade.check behaviour to send back error if schema is out of date, instead of no error and "false".

src/upgrade.js

@@ -34,12 +34,13 @@ Upgrade.check = function(callback) {
 				if (err) {
 					return callback(err);
 				}
-				callback(null, true);
+				callback(null);
 			});
 			return;
 		}
 
-		callback(null, parseInt(value, 10) >= latestSchema);
+		var schema_ok = parseInt(value, 10) >= latestSchema;
+		callback(!schema_ok ? new Error('schema-out-of-date') : null);
 	});
 };