Show full backtrace for Rake test suite failures

Also don't fail fast when running from Rake (e.g. on Travis)
Add docs badge to README
Additional information on upgrading in README
Push release tags to canonical repository
Explicitly require I18n's hash extensions

ActiveSupport 3 doesn't implement `Hash#deep_symbolize_keys`, but I18n does.
Put missing .yml template file in gem
Bump version