when specifying options, the "--no" version of a flag must appear after the flag

We had this problem in visionmedia/mocha#1296.

The below works great:

``` js
  .option('-c, --colors', 'force enabling of colors')
  .option('-C, --no-colors', 'force disabling of colors')
```

In the example below, `--no-colors` does not work:

``` js
  .option('-C, --no-colors', 'force disabling of colors')
  .option('-c, --colors', 'force enabling of colors')
```
