Use http2/hpack fork in http2 fork

vendor/github.com/Psiphon-Labs/net/http2/frame.go

@@ -14,8 +14,8 @@ import (
 	"strings"
 	"sync"
 
+	"github.com/Psiphon-Labs/net/http2/hpack"
 	"golang.org/x/net/http/httpguts"
-	"golang.org/x/net/http2/hpack"
 )
 
 const frameHeaderLen = 9

vendor/github.com/Psiphon-Labs/net/http2/server.go

@@ -46,8 +46,8 @@ import (
 	"sync"
 	"time"
 
+	"github.com/Psiphon-Labs/net/http2/hpack"
 	"golang.org/x/net/http/httpguts"
-	"golang.org/x/net/http2/hpack"
 )
 
 const (

vendor/github.com/Psiphon-Labs/net/http2/transport.go

@@ -28,8 +28,8 @@ import (
 	"sync"
 	"time"
 
+	"github.com/Psiphon-Labs/net/http2/hpack"
 	"golang.org/x/net/http/httpguts"
-	"golang.org/x/net/http2/hpack"
 	"golang.org/x/net/idna"
 )
 

vendor/github.com/Psiphon-Labs/net/http2/write.go

@@ -11,8 +11,8 @@ import (
 	"net/http"
 	"net/url"
 
+	"github.com/Psiphon-Labs/net/http2/hpack"
 	"golang.org/x/net/http/httpguts"
-	"golang.org/x/net/http2/hpack"
 )
 
 // writeFramer is implemented by any type that is used to write frames.

vendor/vendor.json

@@ -62,6 +62,12 @@
 			"revision": "03e6572170e3643a5cf49ef0a0ce746e53b63cf3",
 			"revisionTime": "2018-09-12T16:47:43Z"
 		},
+		{
+			"checksumSHA1": "DyTNDdPyzkdNw1Ao0HiRbI3hQI8=",
+			"path": "github.com/Psiphon-Labs/net/http2/hpack",
+			"revision": "03e6572170e3643a5cf49ef0a0ce746e53b63cf3",
+			"revisionTime": "2018-09-12T16:47:43Z"
+		},
 		{
 			"checksumSHA1": "DmQc8vfP44VMUTIZJGM4WslOyk0=",
 			"path": "github.com/Psiphon-Labs/tls-tris",
@@ -645,13 +651,6 @@
 			"revision": "8a410e7b638dca158bf9e766925842f6651ff828",
 			"revisionTime": "2018-08-25T16:15:26Z"
 		},
-		{
-			"checksumSHA1": "KZniwnfpWkaTPhUQDUTvgex/7y0=",
-			"path": "golang.org/x/net/http2/hpack",
-			"revision": "8a410e7b638dca158bf9e766925842f6651ff828",
-			"revisionTime": "2018-08-25T16:15:26Z",
-			"versionExact": "release-branch.go1.9"
-		},
 		{
 			"checksumSHA1": "1osdKBIU5mNqyQqiGmnutoTzdJA=",
 			"path": "golang.org/x/net/idna",