Release 2.1

And here's the latest ibus-cangjie release.

The changes in this version are:
* Add a link to the release tarballs in the README (Mathieu)
* Actually run the unit tests on « make check » (Anthony)
* Improve « make clean » (Anthony)
* Add install instructions for a few distributions (Mathieu)
* Improve the optionality of pycanberra (Mathieu)
* Fix the pt_BR translation (Mathieu)
* Reset sys.path to limit side effects on the unit tests (Mathieu)
* Ensure validity of the preferences UI file (Mathieu)
* Fix the UI file (Mathieu)

Users are **highly** encouraged to upgrade.

Happy Chinese New Year!