Migrate from github.com/stretchrcom/testify to
github.com/stretchr/testify

The author has changed his name.

Fixes #26
diff --git a/diffmatchpatch/dmp_test.go b/diffmatchpatch/dmp_test.go
index c599ecb..403166c 100644
--- a/diffmatchpatch/dmp_test.go
+++ b/diffmatchpatch/dmp_test.go
@@ -11,7 +11,7 @@
 	"time"
 	"unicode/utf8"
 
-	"github.com/stretchrcom/testify/assert"
+	"github.com/stretchr/testify/assert"
 )
 
 func caller() string {