contrib_bots: Restructure bots to follow a consistent structure.

Now all the bots that are stored in contrib_bots are in the
same file/directory format.
The format is specified here #3427. Add tests.py file for encrypt_bot as well.
Fixes #3427.

contrib_bots/bots/converter/tests.py

@@ -20,6 +20,7 @@ def test():
                 expected: %s
                 but got : %s
                 ''' % (cmd, expected_response, client_dummy.output))
+
 def sample_conversation():
     return [
         ('@convert 2 m cm', '2.0 m = 200.0 cm\n'),