vendor: update all dependencies

* Update all dependencies
  * Remove all `[[constraint]]` from Gopkg.toml
  * Add in the minimum number of `[[override]]` to build
  * Remove go get of github.com/inconshreveable/mousetrap as it is vendored
  * Update docs with new policy on constraints

vendor/golang.org/x/net/icmp/message_test.go

@@ -76,6 +76,18 @@ func TestMarshalAndParseMessage(t *testing.T) {
 						Data: []byte("HELLO-R-U-THERE"),
 					},
 				},
+				{
+					Type: ipv4.ICMPTypeExtendedEchoRequest, Code: 0,
+					Body: &icmp.ExtendedEchoRequest{
+						ID: 1, Seq: 2,
+					},
+				},
+				{
+					Type: ipv4.ICMPTypeExtendedEchoReply, Code: 0,
+					Body: &icmp.ExtendedEchoReply{
+						State: 4 /* Delay */, Active: true, IPv4: true,
+					},
+				},
 				{
 					Type: ipv4.ICMPTypePhoturis,
 					Body: &icmp.DefaultMessageBody{
@@ -120,6 +132,18 @@ func TestMarshalAndParseMessage(t *testing.T) {
 						Data: []byte("HELLO-R-U-THERE"),
 					},
 				},
+				{
+					Type: ipv6.ICMPTypeExtendedEchoRequest, Code: 0,
+					Body: &icmp.ExtendedEchoRequest{
+						ID: 1, Seq: 2,
+					},
+				},
+				{
+					Type: ipv6.ICMPTypeExtendedEchoReply, Code: 0,
+					Body: &icmp.ExtendedEchoReply{
+						State: 5 /* Probe */, Active: true, IPv6: true,
+					},
+				},
 				{
 					Type: ipv6.ICMPTypeDuplicateAddressConfirmation,
 					Body: &icmp.DefaultMessageBody{