Changed db schema, table "note", column "title", type from "character varying(256)" to "text".

To make very long title possible

hackmd_schema.sql

@@ -37,7 +37,7 @@ CREATE TABLE notes (
     id character varying(256) NOT NULL,
     owner character varying(256) NOT NULL,
     content text,
-    title character varying(256),
+    title text,
     create_time timestamp without time zone DEFAULT now() NOT NULL,
     update_time timestamp without time zone DEFAULT now() NOT NULL
 );