Add null encoding when writing to streams on close

- Fixes jasmine/jasmine#1622

Author: Gregg Van Hove

lib/jasmine.js

@@ -207,7 +207,7 @@ Jasmine.prototype.exitCodeCompletion = function(passed) {
   var streams = [process.stdout, process.stderr];
   var writesToWait = streams.length;
   streams.forEach(function(stream) {
-    stream.write('', exitIfAllStreamsCompleted);
+    stream.write('', null, exitIfAllStreamsCompleted);
   });
   function exitIfAllStreamsCompleted() {
     writesToWait--;