Make most of the application actually use the I18n config

There are still some remnants of user-facing strings in the templates,
like "Listing Users" and links like "show" and "edit." Most of these
things, however, are now removed
Make the current_user parameter persistent

This makes sure that if you pass ?current_user=username your current
login is saved into the session, so it is also valid on subsequent
requests without the current_user parameter.

Logging out can be done by adding ?current_user=
Dynamically generate a secret token if none exists

Closes #24
Merge branch 'master' into features/correct_i18n

Conflicts:
	config/initializers/secret_token.rb
Remove unneeded quotes from i18n config files

Consistency is nice.