tree: Remove superfluous ' in panic reason

tree.go

diff --git a/tree.go b/tree.go
index ef9d564..1f4f995 100644
--- a/tree.go
+++ b/tree.go
@@ -153,9 +153,10 @@
 						pathSeg := strings.SplitN(path, "/", 2)[0]
 						prefix := fullPath[:strings.Index(fullPath, pathSeg)] + n.path
 						panic("'" + pathSeg +
-							"' in new path '" + fullPath + "'" +
+							"' in new path '" + fullPath +
 							"' conflicts with existing wildcard '" + n.path +
-							"' in existing prefix '" + prefix + "'")
+							"' in existing prefix '" + prefix +
+							"'")
 					}
 				}