For spanish models, inherit from english models

[jinpark]

AFAIK, there are no real differences between the spanish and english models, so instead of just copy and pasting and then forgetting to update one when the other changes, instead the spanish one can inherit from the engish model

More info https://docs.djangoproject.com/en/1.9/topics/db/models/#model-inheritance
Take a look at the examples there

cc @RachellCalhoun

[RachellCalhoun]

I think we're gonna scrap this idea. Unless someone wants to tackle it. I tried but got stuck.