reduce data duplication by removing line numbers from PO files
reorganize the i18n files
remove partial chinese translation
don't omit header, transifex needs it
use transifex-client to upload and download translations
don't keep the dates in the PO files, they'd generate git noise
first run of `make i18n_download`
sync translations as part of the release process
automatically fetch transifex credentials from heroku
add a note about the translation process
Merge pull request #2831 from gratipay/i18n-transifex

Use transifex for i18n