Provide a description of the timeout error

lib/couchrest/monkeypatches.rb

@@ -39,7 +39,7 @@ if RUBY_VERSION.to_f < 1.9
           if IO.select([@io], nil, nil, @read_timeout)
             retry
           else
-            raise Timeout::Error
+            raise Timeout::Error, "IO timeout"
           end
         end
       else