Compliance helpers

@fancyremarker  This, depends on #14 first

The main idea here is to generalize some of the helpers inside dashboard so they may be used in the compliance apps.

What do you think about the change to `register_url` inside view_helper.rb?  This allows all apps to share common header partials without defined routes for orgs/users.


This is used just for integer timestamps coming back from Stripe currently? If any `aptible-resource`-based gem isn't sending dates back as `DateTime`, it's a bug and I'll fix.

Generally I think putting these time helpers in `aptible-rails` is a good idea. Eventually, I'd like to have all time formatting decisions (e.g., do we list a date, or use `time_ago_in_words`, etc.) here.