Added ability to run interactively with arguments

There currently is no way to run node interactively and pass arguments without
a file: `node -i foo bar baz` will instruct node to load `foo`.

This commit adds a `--` argument that instructs node to run interactive and not
to load any file in the argv:

    $ node -i -- foo bar baz
    > process.argv
    [ '/the/path/to/node',
      '--',
      'foo',
      'bar',
      'baz' ]

The same thing works without the '-i':

    $ node -- foo bar baz
    > process.argv
    [ '/the/path/to/node',
      '--',
      'foo',
      'bar',
      'baz' ]