Add translation framework

Hi Trey,

these are the changes that are done in the listet commits:

- add calls to ugettext_lazy to `Email` model
- add `verbose_name`s to `Email` model and to each of its fields
- add language files for English (source language) and German
- add configuration for project at [Transifex](https://www.transifex.com/projects/p/django-email-log/) to make adding other languages more convenient

I also sent you a request to become maintainer of the Transifex project for this app. 

Regards,
Jannis