Add rest parameters syntax for multiple params

Hi!

Rest parameter syntax is coming in EcmaScript 6 (already in Firefox Nightly!). It looks like this:

```JavaScript
function foo(param1, ...args) {
  // args is an array
}
```

I think it makes sense to use this syntax instead of YUIDoc's `*` for multiple parameters. It's easier to remember (I sometimes confuse it with `Type[]`) and maybe some day we'll be using it in real code. This pull request updates the docs to use `...params`, and adds the option for `@param {Type} ...params` and `@param {Type} [...params].`

I added tests for this feature but I can't seem to run them from the command line. Is there anything else I should do besides running `node tests\parser.js`?