Cleanup release

Fixed

• Add / cleanup README
• tests cleanup
• Allow Active Record Ransack aliases with the same name on different models #717
• Use class attributes properly so that inheritance is respected
• use ActiveSupport.on_load to hook into Active Record
• Add custom_arrows config functionality

Thanks

@garettarrowood, @Paxa, @jonatack, @laserlemon, @y-yagi, @jspizziri, @seanfcarroll, @fakefarm, @aspirewit, @mataki