splitter: 1.1.3 - Refined test & fixed a bug in the splitting-pattern

- The tests now sends messages for two users and asserts, that the
  messages are handled accordingly for each user.
- The test now send messages with german umlauts and other special german
  characters.
- Fixed a bug in the pattern, that is used for the spltting: language
  specific special characters were handled as non-word characters.