Fix in demos related to async-await syntax (#123)

- remove 3.4 version from setup.py
- add cryprography package to requirements since it is used in
dictionary_auth
- add a few missed async kwords

demo/database_auth/db_auth.py

@@ -10,7 +10,7 @@ class DBAuthorizationPolicy(AbstractAuthorizationPolicy):
     def __init__(self, dbengine):
         self.dbengine = dbengine
 
-    def authorized_userid(self, identity):
+    async def authorized_userid(self, identity):
         async with self.dbengine as conn:
             where = sa.and_(db.users.c.login == identity,
                             sa.not_(db.users.c.disabled))

demo/database_auth/main.py

@@ -13,7 +13,7 @@ from demo.db_auth import DBAuthorizationPolicy
 from demo.handlers import Web
 
 
-def init(loop):
+async def init(loop):
     redis_pool = await create_pool(('localhost', 6379))
     db_engine = await create_engine(user='aiohttp_security',
                                          password='aiohttp_security',