Nested ordered list numbers don't match GitHub's

[SteeveDroz]

When an ordered list is nested inside another ordered list, the numbers don't behave like they do on GitHub.

Code:

1. Item
    1. Nested Item
        1. Double Nested Item
        2. Double Nested Item
    2. Nested Item
        1. Double Nested Item
        2. Double Nested Item
2. Item
    1. Nested Item
        1. Double Nested Item
        2. Double Nested Item
    2. Nested Item
        1. Double Nested Item
        2. Double Nested Item

On Atom Markdown Preview, it produces:

1. Item
    1. Nested Item
        1. Double Nested Item
        2. Double Nested Item
    2. Nested Item
        1. Double Nested Item
        2. Double Nested Item
2. Item
    1. Nested Item
        1. Double Nested Item
        2. Double Nested Item
    2. Nested Item
        1. Double Nested Item
        2. Double Nested Item

On GitHub, it produces:

1. Item
    i. Nested Item
        a. Double Nested Item
        b. Double Nested Item
    ii. Nested Item
        a. Double Nested Item
        b. Double Nested Item
2. Item
    i. Nested Item
        a. Double Nested Item
        b. Double Nested Item
    ii. Nested Item
        a. Double Nested Item
        b. Double Nested Item

This is not at all a bug, but may I suggest a configuration option that allows to choose which display the user wants?