[Rule] support 1.8

Author: waterlink

lib/rack_reverse_proxy/rule.rb

@@ -64,7 +64,7 @@ def initialize(rule, has_custom_url, path, env, matches)
 
       def build_uri
         return nil unless url
-        URI(raw_uri)
+        raw_uri
       end
 
       private
@@ -100,7 +100,7 @@ def with_substitutions?
       end
 
       def substitute_matches
-        matches.substitute(url)
+        URI(matches.substitute(url))
       end
     end