implement to_a and to_ary so that the Array() call in template.rb will

not raise so many exceptions:

  https://github.com/rails/rails/blob/master/actionpack/lib/action_view/template.rb#L126

irb(main):001:0> class Foo; def method_missing(*args); super; end end
=> nil
irb(main):002:0> $DEBUG = true
=> true
irb(main):003:0> Array(Foo.new)
Exception `NoMethodError' at (irb):1 - undefined method `to_ary' for #<Foo:0x007f854390e488>
Exception `NoMethodError' at (irb):1 - undefined method `to_a' for #<Foo:0x007f854390e488>
=> [#<Foo:0x007f854390e488>]
irb(main):004:0>

actionpack/lib/action_dispatch/http/mime_type.rb

@@ -288,7 +288,12 @@ module Mime
       @@html_types.include?(to_sym) || @string =~ /html/
     end
 
+
     private
+
+    def to_ary; end
+    def to_a; end
+
     def method_missing(method, *args)
       if method.to_s.ends_with? '?'
         method[0..-2].downcase.to_sym == to_sym