[1.8 compatibility] there is no #each_with_object

Author: waterlink

.rubocop.yml

@@ -13,3 +13,6 @@ Style/Lambda:
 
 Style/TrailingComma:
   EnforcedStyleForMultiline: no_comma
+
+Style/EachWithObject:
+  Enabled: false

lib/rack_reverse_proxy/middleware.rb

@@ -144,9 +144,10 @@ def reverse_proxy(matcher, url = nil, opts = {})
     end
 
     def format_headers(headers)
-      headers.each_with_object({}) do |(key, val), acc|
+      headers.inject({}) do |acc, (key, val)|
         formated_key = key.split("-").map(&:capitalize).join("-")
         acc[formated_key] = Array(val)
+        acc
       end
     end
   end