separate game logic from bot interface,

introduce exceptions instead of boolean returns,
remove repetitive code,
begin unit tests,
improve docstrings,
update to python-telegram-bot==4.1.1,
add ponyorm settings classes (unused)

database.py

@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+#
+# Telegram bot to play UNO in group chats
+# Copyright (c) 2016 Jannes Höke <uno@jhoeke.de>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 of the
+# License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+
+from pony.orm import Database, db_session, Optional, Required, Set, PrimaryKey
+
+# Database singleton
+db = Database()