Initial support for getting the leader from Zookeeper.

Some tests included for making sure the JSON blob pulled from Zookeeper
is correct.

Updated client to be able to take Zookeeper json cluster config that is
currently being used in aurora (clusters.json usually located at
/etc/aurora/cluster.json).

Changed error messages to no longer have a period at the end as that was
throwing off printing of the error.

Modified samuel's ZK library slightly to stop verbose logging using a
NoOpLogger from stackoverflow.

vendor/github.com/samuel/go-zookeeper/zk/util.go

@@ -0,0 +1,54 @@
+package zk
+
+import (
+	"crypto/sha1"
+	"encoding/base64"
+	"fmt"
+	"math/rand"
+	"strconv"
+	"strings"
+)
+
+// AuthACL produces an ACL list containing a single ACL which uses the
+// provided permissions, with the scheme "auth", and ID "", which is used
+// by ZooKeeper to represent any authenticated user.
+func AuthACL(perms int32) []ACL {
+	return []ACL{{perms, "auth", ""}}
+}
+
+// WorldACL produces an ACL list containing a single ACL which uses the
+// provided permissions, with the scheme "world", and ID "anyone", which
+// is used by ZooKeeper to represent any user at all.
+func WorldACL(perms int32) []ACL {
+	return []ACL{{perms, "world", "anyone"}}
+}
+
+func DigestACL(perms int32, user, password string) []ACL {
+	userPass := []byte(fmt.Sprintf("%s:%s", user, password))
+	h := sha1.New()
+	if n, err := h.Write(userPass); err != nil || n != len(userPass) {
+		panic("SHA1 failed")
+	}
+	digest := base64.StdEncoding.EncodeToString(h.Sum(nil))
+	return []ACL{{perms, "digest", fmt.Sprintf("%s:%s", user, digest)}}
+}
+
+// FormatServers takes a slice of addresses, and makes sure they are in a format
+// that resembles <addr>:<port>. If the server has no port provided, the
+// DefaultPort constant is added to the end.
+func FormatServers(servers []string) []string {
+	for i := range servers {
+		if !strings.Contains(servers[i], ":") {
+			servers[i] = servers[i] + ":" + strconv.Itoa(DefaultPort)
+		}
+	}
+	return servers
+}
+
+// stringShuffle performs a Fisher-Yates shuffle on a slice of strings
+func stringShuffle(s []string) {
+	for i := len(s) - 1; i > 0; i-- {
+		j := rand.Intn(i + 1)
+		s[i], s[j] = s[j], s[i]
+	}
+}