i18nize of the template and the handlebars.

Implementation of #2691 
Hi @aronasorman 
Branch Develop

Implementation of i18n in the handle bars and Django templates.
Some things that need to be changed:

- This looks like a hassle to extend whenever we create a new app. If we wanna go this way, you could just do a `glob.glob` to find all the html and handlebars files, and then pass that to`i18nize-templates`.

- `os.popen` is [deprecated](https://docs.python.org/2/library/os.html#os.popen). Please use `subprocess.call` or `subprocess.Popen`, depending on your needs.

- Use `AppCommand` instead of `BaseCommand` if you're gonna use an app name as argument. That should handle your else statement.