Always send Content-Length header. Fixes compatibility issues with elasticsearch behind nginx.

See https://github.com/elastic/cookbook-elasticsearch/issues/38 or http://serverfault.com/questions/164220/is-there-a-way-to-avoid-nginx-411-content-length-required-errors

src/lib/connectors/http.js

@@ -185,10 +185,11 @@ HttpConnector.prototype.request = function (params, cb) {
     request.setHeader('Content-Length', Buffer.byteLength(params.body, 'utf8'));
     request.end(params.body);
   } else {
+    request.setHeader('Content-Length', 0);
     request.end();
   }
 
   return function () {
     request.abort();
   };
-};
+};