nil instead of raise

[AlexLarra]

Hi grosser,
I needed a list of languages translated in their own language and I used your gem. I did this helper.

def languages
  languages = {}

  I18nData.languages.each do |code, language|
    begin
      languages.merge!(I18nData.languages(code)[code] => code.downcase)
    rescue Exception => e
      languages.merge!(I18nData.languages('EN')[code] => code.downcase)
    end
  end
  languages
end

It would better not to work with rescue but there it is this line that uses raises instead of return nil:

i18n_data/lib/i18n_data/file_data_provider.rb

Line 8 in b9d0db3

raise NoTranslationAvailable, "#{type}-#{language_code}"

Wouldn't be better to use nil?

Thank you for your gem

[grosser]

sounds like a good idea, can you make this a PR ?