Update README.md with a link to the relevant paper.
Add the hash code and some basic tests.

A valid TODO would be adding tests that verify behavior as bucket size changes, etc. This is okay to start with I suppose.

$ go test
PASS
ok      jump-consistent-hash    0.008s
$ go test --bench=.
PASS
BenchmarkHash   20000000               127 ns/op
ok      jump-consistent-hash    2.673s