Remove diff substring before serializing result for GoConvey UI.

serializer.go

diff --git a/serializer.go b/serializer.go
index fa32f94..f1e3570 100644
--- a/serializer.go
+++ b/serializer.go
@@ -3,6 +3,7 @@
 import (
 	"encoding/json"
 	"fmt"
+	"strings"
 
 	"github.com/smartystreets/assertions/internal/go-render/render"
 )
@@ -15,6 +16,9 @@
 type failureSerializer struct{}
 
 func (self *failureSerializer) serializeDetailed(expected, actual interface{}, message string) string {
+	if index := strings.Index(message, " Diff:"); index > 0 {
+		message = message[:index]
+	}
 	view := FailureView{
 		Message:  message,
 		Expected: render.Render(expected),
@@ -25,6 +29,9 @@
 }
 
 func (self *failureSerializer) serialize(expected, actual interface{}, message string) string {
+	if index := strings.Index(message, " Diff:"); index > 0 {
+		message = message[:index]
+	}
 	view := FailureView{
 		Message:  message,
 		Expected: fmt.Sprintf("%+v", expected),

serializer_test.go

diff --git a/serializer_test.go b/serializer_test.go
index 9ae1836..e081f8a 100644
--- a/serializer_test.go
+++ b/serializer_test.go
@@ -9,13 +9,13 @@
 func TestFailureSerializerCreatesSerializedVersionOfAssertionResult(t *testing.T) {
 	thing1 := Thing1{"Hi"}
 	thing2 := Thing2{"Bye"}
-	message := "Super-hip failure message."
+	message := "Super-hip failure message. Diff: Something that we don't need."
 	serializer := newSerializer()
 
 	actualResult := serializer.serialize(thing1, thing2, message)
 
 	expectedResult, _ := json.Marshal(FailureView{
-		Message:  message,
+		Message:  "Super-hip failure message.",
 		Expected: fmt.Sprintf("%+v", thing1),
 		Actual:   fmt.Sprintf("%+v", thing2),
 	})
@@ -26,7 +26,7 @@
 
 	actualResult = serializer.serializeDetailed(thing1, thing2, message)
 	expectedResult, _ = json.Marshal(FailureView{
-		Message:  message,
+		Message:  "Super-hip failure message.",
 		Expected: fmt.Sprintf("%#v", thing1),
 		Actual:   fmt.Sprintf("%#v", thing2),
 	})