v2.1

• Add a link to the release tarballs in the README (Mathieu Bridon)
• Actually run the unit tests on « make check » (Anthony Wong)
• Improve « make clean » (Anthony Wong)
• Add install instructions for a few distributions (Mathieu Bridon)
• Improve the optionality of pycanberra (Mathieu Bridon)
• Fix the pt_BR translation (Mathieu Bridon)
• Reset sys.path to limit side effects on the unit tests (Mathieu Bridon)
• Ensure validity of the preferences UI file (Mathieu Bridon)
• Fix the UI file (Mathieu Bridon)