Optimized ip checking algorithm for ipv6

[oldthreefeng]

Benchmark, 使用正则的速度是比较慢的. #14

$ go test -v -bench=. -benchtime=3s -benchmem                                
=== RUN   TestIP4Re
[1.1.11.23 36.36.32.200]
false
--- PASS: TestIP4Re (0.00s)
=== RUN   TestValidIP6
--- PASS: TestValidIP6 (0.00s)
goos: linux
goarch: amd64
pkg: github.com/zu1k/nali/internal/tools
BenchmarkValidIP6Re
BenchmarkValidIP6Re-8             807940              4429 ns/op              32 B/op          1 allocs/op
BenchmarkValidIP6
BenchmarkValidIP6-8              9549422               362 ns/op             160 B/op          3 allocs/op
PASS
ok      github.com/zu1k/nali/internal/tools     7.476s

[oldthreefeng]

golang/go#6628 这个没有判断, 加上了

[zu1k]

非常感谢:+1: