add JWTIdentityPolicy into __init__ file. (#157)

Author: alexpantyukhin

aiohttp_security/__init__.py

@@ -3,12 +3,14 @@
                   login_required, permits, remember, setup)
 from .cookies_identity import CookiesIdentityPolicy
 from .session_identity import SessionIdentityPolicy
+from .jwt_identity import JWTIdentityPolicy
 
 __version__ = '0.2.0'
 
 
 __all__ = ('AbstractIdentityPolicy', 'AbstractAuthorizationPolicy',
            'CookiesIdentityPolicy', 'SessionIdentityPolicy',
+           'JWTIdentityPolicy',
            'remember', 'forget', 'authorized_userid',
            'permits', 'setup', 'is_anonymous',
            'login_required', 'has_permission')