Fixed #13, eventually crash when elasticsearch connection error

Author: Felix

lib/es-proxy.js

@@ -37,6 +37,11 @@ function proxyRequest(request, response, host, port, user, password, getProxiedR
 
   var proxyReq = http.request(options);
 
+  proxyReq.addListener('error', function(err){
+    response.status(500).send('Unable to process your request, ' + err.code);
+    console.log('ElasticSearch Server Error: ' + err.code);
+  });
+
   proxyReq.addListener('response', function(proxyResp) {
     var http10 = request.httpVersionMajor === 1 && request.httpVersionMinor < 1;
     if(http10 && proxyResp.headers['transfer-encoding'] !== undefined){