Fix #11 . balance second-level nodes automatically
update
support shortcut for add child_node/borther_node
add new utility method: jm.util.json.merge
edit some method
for up/down shortcut, not complete
resolve #6, provide shortcut for operate mind.(eg: add,remove,left,right,toggle)
Merge branch 'master' into webapp
Merge branch 'webapp' into gh-pages