Format cookie 'Expires' timestamps as per RFC 2616

For reference:
 - https://www.rfc-editor.org/rfc/rfc2616#section-3.3.1
 - https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Expires

Author: orien

lib/webmachine/cookie.rb

@@ -102,10 +102,12 @@ def to_s
 
     private
 
+    # Format timestamps for the 'Expires' portion of the cookie string, as per RFC 2822 and 2616.
+    #
+    # @see https://www.rfc-editor.org/rfc/rfc2616#section-3.3.1
+    # @see https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Expires
     def rfc2822(time)
-      wday = Time::RFC2822_DAY_NAME[time.wday]
-      mon = Time::RFC2822_MONTH_NAME[time.mon - 1]
-      time.strftime("#{wday}, %d-#{mon}-%Y %H:%M:%S GMT")
+      time.strftime('%a, %d %b %Y %T GMT')
     end
 
     if URI.respond_to?(:decode_www_form_component) and defined?(::Encoding)

spec/webmachine/cookie_spec.rb

@@ -60,7 +60,7 @@
         expect(str).to include "Path=/"
         expect(str).to include "Version=1"
         expect(str).to include "Max-Age=60"
-        expect(str).to include "Expires=Sun, 14-Mar-2010 03:14:00 GMT"
+        expect(str).to include "Expires=Sun, 14 Mar 2010 03:14:00 GMT"
       end
     end
   end