update to V1.2

V1.2 Changelist:
1. add Tag support.
2. add shortcuts support.
3. add like/unlike for photo and comment.
4. fixed BAE issue "mySQL gone away".

V1.1 Changelist:
1. add GAE support.
2. add memcache support.
3. add i18n support.
4. add auto-migrate support.
5. enhance MarkDown editor.
6. fixed some bugs.