Be explit about binding only default vector allocator
diff --git a/src/cxx_vector.rs b/src/cxx_vector.rs
index f7fb5ac..8a73c7e 100644
--- a/src/cxx_vector.rs
+++ b/src/cxx_vector.rs
@@ -1,6 +1,6 @@
 use std::mem;
 
-/// Binding to C++ `std::vector<T>`.
+/// Binding to C++ `std::vector<T, std::allocator<T>>`.
 ///
 /// # Invariants
 ///