Pull latest Transifex .po files

It looks like 0.6 was missing some translation files due to a bug in the
Transifex client which was tricked by local timestamps and skipping some
translation files:
https://github.com/transifex/transifex-client/issues/22

We need to remember to use `tx pull -af` next time to force the download
of .po files.
Bump version to 0.6.1