introduce docs -> models section mostly finished

docs_src/models/docs004.py

@@ -0,0 +1,22 @@
+import databases
+import sqlalchemy
+
+import orm
+
+database = databases.Database("sqlite:///db.sqlite")
+metadata = sqlalchemy.MetaData()
+
+
+class Course(orm.Model):
+    __database__ = database
+    __metadata__ = metadata
+
+    id = orm.Integer(primary_key=True)
+    name = orm.String(length=100)
+    completed = orm.Boolean(default=False)
+
+print(Course.__table__.columns)
+"""
+Will produce:
+['courses.id', 'courses.name', 'courses.completed']
+"""