Let users choose file extension

[tai2]

I would like to use .pcss instead of .css as the PostCSS organization officially suggests.

What do you think about adding an option to specify file extension?

[joshwnj]

@tai2 sure, I'd be ok with this - and it wouldn't be too hard to introduce that option.

Would you like to try creating a PR for it? I'd be happy to help if you get stuck at any point.

[tai2]

I'll try it. Pleas wait a moment.

[joshwnj]

Thanks @tai2 , this is published to npm as v0.27.0