Change method to output text to stdout without line break.

PhantomJS 1.9.0 implement direct access to stdout via system module.

https://github.com/ariya/phantomjs/issues/10243
(original: http://code.google.com/p/phantomjs/issues/detail?id=243 )

Additional information:
original `fs.write` logic cause error when phantomjs-testrunner.js is launched by grunt-exec task.