Add testable interface for datastore.

doc.go

Index: doc.go
diff --git a/doc.go b/doc.go
index 483b7c0a4cd1b03b4ddbc1e8a80baac2f24bfd35..fb1eac2918ea266107acaf90a8ed260324b30384 100644
--- a/doc.go
+++ b/doc.go
@@ -109,10 +109,10 @@
 //
 //    service.Testable     - any additional methods that a 'testing'
 //                           implementation should provide. This can be accessed
-//                           via the Testable method on Interface or
-//                           RawInterface. If the current implementation is not
-//                           testable, it will return nil. This is only meant to
-//                           be accessed when testing.
+//                           via the Testable method on RawInterface. If the
+//                           current implementation is not testable, it will
+//                           return nil. This is only meant to be accessed when
+//                           testing.
 //
 //    service.RawFactory   - a function returning a RawInterface
 //