Add test to assert cmd2.__version__ exists

Author: kotfu

tests/test_cmd2.py

@@ -28,6 +28,9 @@
     HELP_HISTORY, SHORTCUTS_TXT, SHOW_TXT, SHOW_LONG, StdOut
 
 
+def test_version(base_app):
+    assert cmd2.__version__
+
 def test_empty_statement(base_app):
     out = run_cmd(base_app, '')
     expected = normalize('')