[FEATURE] .by_uuid scope with no arguments returns all records.

  class MyModel < ActiveRecord::Base
    include Uuids::Base
    has_uuids
  end

  MyModel.by_uuids() == MyModel.all
  # => true

  # COMPARE TO OLD VERSIONS (v2.0.0 and earlier):
  # MyModel.by_uuids() # => #<ActiveRecord::Relation []>

== Version

Changed to 3.0.0 (backward incompatible).