Changed from passing strings for network addresses to
pointers to net.IP.  Although the director algorithms were linear before
with a best-fit slope of 354.558, using *net.IP stucts
lowers the slope to 33.815, a 10x improvement.

Before:

BenchmarkDirector1       5000000               352 ns/op
BenchmarkDirector2       5000000               709 ns/op
BenchmarkDirector3       1000000              1064 ns/op
BenchmarkDirector4       1000000              1420 ns/op
BenchmarkDirector5       1000000              1775 ns/op
BenchmarkDirector10       500000              3557 ns/op
BenchmarkDirector100       50000             35457 ns/op

After:

BenchmarkDirector1      50000000                38.3 ns/op
BenchmarkDirector2      50000000                70.3 ns/op
BenchmarkDirector3      20000000               104 ns/op
BenchmarkDirector4      10000000               146 ns/op
BenchmarkDirector5      10000000               180 ns/op
BenchmarkDirector10      5000000               349 ns/op
BenchmarkDirector100      500000              3388 ns/op