IPAddr#mask method accepts arguments other than integers.

IPAddr#mask method expects an integer argument, but it accepts non-integer values (such as floats or arrays) if passed.

ip = IPAddr.new('1.2.3.4')

p ip.mask(0.1)
# => #<IPAddr: IPv4:0.0.0.0/128.0.0.0>
p ip.mask(1.2)
# => #<IPAddr: IPv4:0.0.0.0/192.0.0.0>
p ip.mask(11.3)
# => #<IPAddr: IPv4:1.0.0.0/255.240.0.0>
p ip.mask([])
# => `mask!': undefined method `<' for []:Array (NoMethodError)

So, I think it is better to restrict the arguments of this method to integers and throw an exception if they are not integers.
Like this.

ip = IPAddr.new('1.2.3.4')

p ip.mask(0.1)
# => `mask!': invalid mask 0.1 (IPAddr::InvalidPrefixError)

I'm currently implementing this improvement and want to submit a pull request as a contribute to this repo.
Would this be acceptable?

Inizia dal metodo IPAddr#mask e riproduci gli esempi di float e array dell’issue. La modifica è completata quando gli argomenti non interi generano IPAddr::InvalidPrefixError, mentre le maschere intere continuano a funzionare come previsto.