Update readme.md

[andbad]

Add explanation for RAM_CHECK option in readme.

[kroese]

I really don't want people to skip that check. If the check is too strict, we should reduce the minimum amount a little for example, so that it becomes more reasonable. But I do not want to give instructions how to disable it.

[andbad]

I see your point.
That check doesn't calculate swap space. That's the only option to get the VM to boot on my machine. I thought it would be helpful to have it documented.

By(t)e