Create composer.json

Add composer file to also add this repo in the [Firegento - Magento Module Composer Repository](http://packages.firegento.com/) and install it via composer. If you merge this commit, please also add a release via the [github release management](https://github.com/ffuenf/Alanstorm_Layout-Unremove/releases/new) with version 1.0.1.