Checking in changes prior to tagging of version 2.18.

Changelog diff is:

diff --git a/Changes b/Changes
index 6c3a08d..3f6840a 100644
--- a/Changes
+++ b/Changes
@@ -2,6 +2,13 @@ Revision history for Perl extension Furl

 {{$NEXT}}

+2.18 2013-08-08T07:11:30Z
+
+    - Furl::Response::decoded_content returns undef if user specifies
+      'Accept-Encoding' for data compression. Because content is already
+      inflated, so HTTP::Message::decoded_content failed and return undef.
+      (syohex)
+
 2.17 2013-07-01T03:11:49Z

     - Fix Furl::Request#as_string the request contains ARRAY or HASH.