Add custom tab-size feature

[barbarbar338]

Not a big change, but a nice addition. It allows us to determine what we want instead of using 2 indents in the pretty option.

If we type pretty: true, indent will be 2, but if we type pretty: 4, indent will be 4

[barbarbar338]

Does this package still maintained? Or i'm going to make an extend of it

[joeattardi]

Will try to get this merged soon. Thanks very much!