s/datadog/DataDog/ to correctly reflect module name

Fixes TencentCloud#10

go.mod

@@ -6,7 +6,7 @@ require (
 	github.com/apache/pulsar-client-go/oauth2 v0.0.0-20200803021613-570d5ceffa19
 	github.com/beefsack/go-rate v0.0.0-20180408011153-efa7637bb9b6
 	github.com/bmizerany/perks v0.0.0-20141205001514-d9a9656a3a4b
-	github.com/datadog/zstd v1.4.6-0.20200617134701-89f69fb7df32
+	github.com/DataDog/zstd v1.4.6-0.20200617134701-89f69fb7df32
 	github.com/davecgh/go-spew v1.1.1
 	github.com/gogo/protobuf v1.3.1
 	github.com/golang/protobuf v1.4.2
@@ -16,7 +16,7 @@ require (
 	github.com/kr/pretty v0.2.1 // indirect
 	github.com/linkedin/goavro/v2 v2.9.8
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
-    github.com/modern-go/reflect2 v1.0.1 // indirect
+	github.com/modern-go/reflect2 v1.0.1 // indirect
 	github.com/pierrec/lz4 v2.0.5+incompatible
 	github.com/pkg/errors v0.9.1
 	github.com/prometheus/client_golang v1.7.1