Ranges support about ipaddress

[bjmllr]

It looks like IPAddress::IPv4 just needs succ defined, but for this use case Range#cover? would be a lot faster and already works on 0.8.0.

ip1 = IPAddress('192.168.10.10')
ip2 = IPAddress('192.168.30.40')

ip = IPAddress('192.168.15.20')
outside = IPAddress('192.168.31.20')

(ip1..ip2).cover?(ip) # => true
(ip1..ip2).cover?(outside) # => false

[t3hk0d3]

@bjmllr see PR #27. Adding #succ is worst way possible, since IP-addresses are actually 32-bit/128-bit integers, and Ruby can work in appropriate way with range of integers, you just need to add #to_int methods.