[VOL-2193] Create mocks for Kafka Client and Etcd

This commit consists of:
1) A kafka client mock that implements the kafka client interface
under voltha-lib-go/pkg/kafka/client.go
2) An embedded Etcd server that runs in-process and represents an
Etcd server.

Change-Id: I52a36132568e08c596bb4136918bebcb654a3b99
diff --git a/vendor/github.com/dustin/go-humanize/.travis.yml b/vendor/github.com/dustin/go-humanize/.travis.yml
new file mode 100644
index 0000000..ba95cdd
--- /dev/null
+++ b/vendor/github.com/dustin/go-humanize/.travis.yml
@@ -0,0 +1,21 @@
+sudo: false
+language: go
+go:
+  - 1.3.x
+  - 1.5.x
+  - 1.6.x
+  - 1.7.x
+  - 1.8.x
+  - 1.9.x
+  - master
+matrix:
+  allow_failures:
+    - go: master
+  fast_finish: true
+install:
+  - # Do nothing. This is needed to prevent default install action "go get -t -v ./..." from happening here (we want it to happen inside script step).
+script:
+  - go get -t -v ./...
+  - diff -u <(echo -n) <(gofmt -d -s .)
+  - go tool vet .
+  - go test -v -race ./...