Please add minimum-stability to composer.json

[indrakaw]

Please add this line into composer.json.

"minimum-stability": "dev",

Without this, installing this repo via composer create-project -s dev is impossible.

This has applied on mini3 too: https://github.com/panique/mini3/blob/master/composer.json#L16

Apply this to other repo: mini and mini2 is fine too.