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/_page.py

@@ -0,0 +1,35 @@
+# -*- coding: UTF-8 -*-
+from __future__ import unicode_literals
+
+from ._thread import ThreadType, Thread
+
+
+class Page(Thread):
+    #: The page's custom url
+    url = None
+    #: The name of the page's location city
+    city = None
+    #: Amount of likes the page has
+    likes = None
+    #: Some extra information about the page
+    sub_title = None
+    #: The page's category
+    category = None
+
+    def __init__(
+        self,
+        uid,
+        url=None,
+        city=None,
+        likes=None,
+        sub_title=None,
+        category=None,
+        **kwargs
+    ):
+        """Represents a Facebook page. Inherits `Thread`"""
+        super(Page, self).__init__(ThreadType.PAGE, uid, **kwargs)
+        self.url = url
+        self.city = city
+        self.likes = likes
+        self.sub_title = sub_title
+        self.category = category