I was reading a lot about translations and language packs, starting at http://devdocs.magento.com/guides/v2.0/config-guide/cli/config-cli-subcommands-i18n.html#config-cli-....
Also, I've checked a few language packs created by community members (i.e.: https://github.com/lalbert/magento2-fr_fr)
Then I've created my own package (https://github.com/barbanet/magento2-language-es_ar) (I've sent the package to Packagist)
I'm not sure if I'm the problem trying to understand the documentation but someone can confirm that there are to steps that are necessary to start to use the translation?
Once we got the package we need to run this commands:
1) Pack the package
bin/magento i18n:pack --mode=merge -d vendor/barbanet/magento2-language-es_ar/es_ar.csv . es_AR
(http://devdocs.magento.com/guides/v2.0/config-guide/cli/config-cli-subcommands-i18n.html#config-cli-...)
2) Generate the files
bin/magento setup:static-content:deploy es_AR
Only after those steps the package has started to work for me.
I'm doing this in the right way?