Split models.py into several files (#398)

* Move exception models into separate file
* Move thread model into separate file
* Move user model into separate file
* Move group and room models into separate file
* Move page model into separate file
* Move message model into separate file
* Move basic attachment models into separate file
* Move sticker model into separate file
* Move location models into separate file
* Move file attachment models into separate file
* Move mention model to reside with message model
* Move quick reply models into separate file
* Move poll models into separate file
* Move plan model into separate file
* Move active status model to reside with user model
* Move core enum model into separate file
* Move thread-related enums to reside with thread model
* Move typingstatus model to reside with user model
* Move emojisize and reaction enums to reside wtih message model

fbchat/__init__.py

@@ -7,6 +7,7 @@
 
 from __future__ import unicode_literals
 
+from .models import *
 from .client import *
 
 __title__ = "fbchat"