project default settings.
make models/tutorials.py
list models related to tutorial.
prototype of model, serializer, view set for tutorials.
prototype of model, serializer, view set for documents.
prototype of model, serializer, view set for bubbles.
prototype of model, serializer, view set for speeches.

delete models(Target, Offset).
change db backends from sqlite3 to mysql.
add nested viewset api.
change variable names more explicit way.
from head to title
from body to description
install south
Merge branch 'default' into tutorial
add files under migrations folder to the gitignore.
Merge branch 'default' into tutorial
add prev attribute to Bubble class.
prototype of model, serializer, view set for feedbacks.
add router for feedbacks.
prototype of model, serializer, view set for comments.
add router for comments.
add fields star and like to Tutorial model.
change url of router.