Adding page titles

The idea is taken from [1] although I don't like the need for the `to_s` method
everywhere. On [2] they expose a better way, passing an object (not just a string)
and calling methods on it, but for some reason it's not working for me.

[1]:http://opensoul.org/2012/11/05/abusing-rails-i18n-to-set-page-titles/
[2]:http://robots.thoughtbot.com/better-tests-through-internationalization