add favicon
change cdn of jquery and bootstrap
1st version of UI, enable tornado debug, add x-editable js&css
add and modify jquery.contenteditable.js lib

remove the "keyup paste" event
finish update operation.

1. abandom x-editable lib because of its poor personalization ability,
e.g. hard to change the size of textarea

2. todo item will be deleted automatically if the content is empty

3. support rich-text todo, basically all html or css

TODO: filter the rich text todo for malicious script