[cmake] I forgot to add the std-array.hpp header...

CMakeLists.txt

@@ -162,6 +162,7 @@ set(${PROJECT_NAME}_HEADERS
     include/eigenpy/user-type.hpp
     include/eigenpy/ufunc.hpp
     include/eigenpy/register.hpp
+    include/eigenpy/std-array.hpp
     include/eigenpy/std-map.hpp
     include/eigenpy/std-vector.hpp
     include/eigenpy/optional.hpp