[BUG] upgrade to version 1.8.4 breaks our translation logic

[stereosupersonic]

What I tried to do

we use our own fallback class for some custom translation logic:

class I18n::OurFallback
  def [](key)
      ... 
  end
end

I18n.fallbacks = I18n::OurFallback.new

this class is not used any more because of this change here

i18n/lib/i18n/backend/fallbacks.rb

Line 23 in 71a51b3

@@fallbacks = fallbacks.is_a?(I18n::Locale::Fallbacks) ? fallbacks : I18n::Locale::Fallbacks.new(fallbacks)

is it possible to fix #534 with the other way around:

  def fallbacks=(fallbacks)
      @@fallbacks = fallbacks.is_a?(Array) ?  I18n::Locale::Fallbacks.new(fallbacks) : fallbacks
   end

thx, i'll prepare a PR for a possible fix