Bunch of updates

[1999]

• Remove domain module usage. This module is long time deprecated and it's not recommended for usage (link 1, link 2, link 3). Also if error occurs inside worker it will be disconnected and re-forked.
• Add 4th option isListening to MC.createHttpServer so that it can be used as a 100% replacement of http.createServer or expressApp.listen (supports all of their API)
• Document isCluster option
• Use node.js assert instead of if..throw - this makes the code cleaner
• Refactoring (counter renamed to counterReloadWorkerFails, noop used instead of empty functions)
• Misc

[jtblin]

Thanks a ton for the PR! I knew domain was deprecated and wanted to remove it for a while. Unfortunately there's no replacement yet but as you indicated if a worker crashes, it will be restarted anyway.