Revise the code to be able to work with django project having multiple app modules

[RuikeYuan]

Test code with some projects from Github.
Revise the script to make models extracting process generic(not 'shared_models' instead to detect if it is an app module folder)
Use double for-loop or whatever to extract classes in models.py of each app module.
Combine the extracted classes and parse into the json.