make sure appium won't run under sudo. Too many people run into problems with that

lib/server/main.js

@@ -14,6 +14,15 @@ if (require.main === module) {
 
 logger = logFactory.get('appium');
 
+if (typeof process.env.SUDO_UID !== "undefined") {
+  logger.error("Appium will not function correctly if used under sudo. " +
+               "Please rerun as a non-root user. If you had to install " +
+               "Appium using `sudo npm install -g appium`, the solution " +
+               "is to reinstall Node using a method (Homebrew, for example) " +
+               "that doesn't require sudo to install global npm packages.");
+  process.exit(1);
+}
+
 var http = require('http')
   , express = require('express')
   , path = require('path')