don't send file in HEAD requests

in current nodes, doing so will raise an exception at which point the
file will never be closed. This leads to file handle starvation sooner
or later

lib/paperboy.js

@@ -47,7 +47,7 @@ exports.streamFile = function (filepath, headerFields, stat, res, req, emitter)
     res.writeHead(statCode, headerFields);
 
     //If we sent a 304, skip sending a body
-    if (statCode == 304) {
+    if (statCode == 304 || req.method === 'HEAD') {
       res.end();
       emitter.emit("success", statCode);
     }