Refactored Rack::Request#media_type

No need for subscript, first reads better

Signed-off-by: Christian Neukirchen <chneukirchen@gmail.com>

lib/rack/request.rb

@@ -46,7 +46,7 @@ def content_type;    @env['CONTENT_TYPE']                     end
     # For more information on the use of media types in HTTP, see:
     # http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.7
     def media_type
-      content_type && content_type.split(/\s*[;,]\s*/, 2)[0].downcase
+      content_type && content_type.split(/\s*[;,]\s*/, 2).first.downcase
     end
 
     # The media type parameters provided in CONTENT_TYPE as a Hash, or