Key? will check existance of key

k = Asetus.new
k = k.cfg
k.foo.bar = 'fum'

This _MUST_ work, so 'k.foo' cannot return nil/false, so I cannot do:

if k.foo.bar
  puts 'we did configure it'
end

But obviously this is super important use_case, we could do this:

if k.foo.key? bar
  puts 'we did configure it'
end

But I think it's not very nice, better way to do it:

if k.foo.bar?
  puts 'we did configure it'
end
bump up gemspec