Update readme.md

    If `kvm-ok` returns an error stating KVM acceleration cannot be used, you may need to change your BIOS settings.

  * ### How do I change the size of the virtual disk? ###

  * ### How do I change the bootdisk? ###

    You can modify the `BOOT` setting to specify the URL of any ISO image:

    ```

    environment:

      BOOT: "http://www.example.com/image.iso"

    ```

    It will be downloaded only once, during the first run of the container.

  * ### How do I change the size of the data disk? ###

    By default it is 16GB, but you can modify the `DISK_SIZE` setting in your compose file:

    To resize the disk to a capacity of 8 terabyte you would use a value of `"8T"` for example.

  * ### How do I change the location of the virtual disk? ###

  * ### How do I change the location of the data disk? ###

    By default it resides inside a docker volume, but you can add these lines to your compose file: