* Update Slack notification to always notify.
* Add optional parameter to `tx-pull-www` to pull just resources for a particular language. Helpful when validations are failing for one language.
* tx-pull-www: pull www translations from transifex
* validate-www: check www for correct placeholders
* add commands to pull and validate www to package.json
* add validating www to the test step
* add pulling www to the update-translations script for the cron job
* changed .tx/config to match the new folder names `scratch-website.<resource-slug>`, and added missing folders. This isn’t needed for the scripts, but it’s useful if you need to pull the translation for a single language/resource
