fix python 2.6 unitests which with the backport package unittest2

.travis.yml

@@ -9,6 +9,7 @@ python:
 install:
   - pip install pylint flake8 coveralls
   - pip install -r requirements.txt
+  - 'if [[ $TRAVIS_PYTHON_VERSION == 2.6 ]]; then pip install unittest2; fi'
 script:
   - nosetests --with-coverage --cover-package telegram/
   - flake8 telegram

tests/test_bot.py

@@ -20,9 +20,14 @@
 """This module contains a object that represents Tests for Telegram Bot"""
 
 import os
-import unittest
 from datetime import datetime
 import sys
+
+if sys.version_info[0:2] == (2, 6):
+    import unittest2 as unittest
+else:
+    import unittest
+
 sys.path.append('.')
 
 import telegram