Fix for-in issue

Signed-off-by: Fabio José <fabiojose@gmail.com>

lib/bindings/http/binary_0_2.js

@@ -36,8 +36,10 @@ HTTPBinary.prototype.emit = function(cloudevent){
   // Have extensions?
   var exts = cloudevent.getExtensions(); 
   for(var ext in exts){
+    if({}.hasOwnProperty.call(exts, ext)){
       _headers["ce-" + ext] = exts[ext];
     }
+  }
 
   // Return the Promise
   return axios.request(_config);