Add minimal MurmurHash2 impl for partitioner (#67)

* Add minimal MurmurHash2 impl for partitioner

Copied from https://github.com/burdiyan/kafkautil/blob/3e3bfeae0ffaf3b3d9b431463d9e58f840173188/partitioner.go

* Add tests

go.mod

@@ -4,15 +4,10 @@ go 1.15
 
 require (
 	github.com/Shopify/sarama v1.29.0
-	github.com/avast/retry-go v3.0.0+incompatible // indirect
-	github.com/burdiyan/kafkautil v0.0.0-20190131162249-eaf83ed22d5b
 	github.com/frankban/quicktest v1.13.0
 	github.com/google/go-cmp v0.5.6
 	github.com/heetch/kafkatest v1.1.0
-	github.com/lovoo/goka v1.0.5 // indirect
 	github.com/pkg/errors v0.9.1
 	github.com/rogpeppe/fastuuid v1.2.0
 	github.com/stretchr/testify v1.7.0
 )
-
-// replace github.com/Shopify/sarama => /home/rog/src/go/src/github.com/Shopify/sarama