add startIndexesFromOne option (false by default)

[yashaka]

so instead this:

    await stage.goto('http://todomvc.com/examples/emberjs');

    await stage.$('#new-todo').type('a').then(perform.press('Enter'));
    await stage.$('#new-todo').type('b').then(perform.press('Enter'));

    await stage.$$('#todo-list li').first.$('.toggle').click();
    await stage.$$('#todo-list li').$(1).$('.toggle').click();
    await stage.$$('#todo-list li').by(have.cssClass('completed'))
      .should(have.texts('a', 'b'));

you can write it like:

    await stage.goto('http://todomvc.com/examples/emberjs');

    await stage.$('#new-todo').type('a').then(perform.press('Enter'));
    await stage.$('#new-todo').type('b').then(perform.press('Enter'));

    await stage.$$('#todo-list li').first.$('.toggle').click();
    await stage.$$('#todo-list li').$(2).$('.toggle').click();
    await stage.$$('#todo-list li').by(have.cssClass('completed'))
      .should(have.texts('a', 'b'));