Manager crashes when selenium environment is unavailable.

When connecting to a selenium grid who has no available environment queen crashes with the following stack trace:

/home/blayne/workspace/js-test/queen-populator-plugin/lib/manager.js:155
				client.on('dead', function(){
				       ^
TypeError: Object #<Object> has no method 'on'
    at Manager.autoSpawnClients.populators.forEach.populator.clients (/home/blayne/workspace/js-test/queen-populator-plugin/lib/manager.js:155:12)
    at createSeleniumClient (/home/blayne/workspace/js-test/queen-populator-plugin/lib/selenium.js:59:4)
    at Request.webdriver.init [as _callback] (/home/blayne/workspace/js-test/queen-populator-plugin/node_modules/wd/lib/webdriver.js:252:9)
    at Request.init.self.callback (/home/blayne/workspace/js-test/queen-populator-plugin/node_modules/wd/node_modules/request/main.js:122:22)
    at Request.EventEmitter.emit (events.js:99:17)
    at Request.<anonymous> (/home/blayne/workspace/js-test/queen-populator-plugin/node_modules/wd/node_modules/request/main.js:661:16)
    at Request.EventEmitter.emit (events.js:126:20)
    at IncomingMessage.Request.start.self.req.self.httpModule.request.buffer (/home/blayne/workspace/js-test/queen-populator-plugin/node_modules/wd/node_modules/request/main.js:623:14)
    at IncomingMessage.EventEmitter.emit (events.js:126:20)
    at IncomingMessage._emitEnd (http.js:366:10)


This seems to be caused by the createSeleniumClient, calling callback(), when it should be passing a Error object into the callback.