Trivial change.

yaml.go

diff --git a/yaml.go b/yaml.go
index bc5cc73..c0423d1 100644
--- a/yaml.go
+++ b/yaml.go
@@ -148,7 +148,7 @@
 // --------------------------------------------------------------------------
 // Maintain a mapping of keys to structure field indexes
 
-// The code in this section was copied from gobson.
+// The code in this section was copied from mgo/bson.
 
 // structInfo holds details for the serialization of fields of
 // a given struct.