Address Frank's comments

gtsam/base/make_shared.h

@@ -17,24 +17,24 @@
 
 #pragma once
 
-#include <boost/make_shared.hpp>
 #include <gtsam/base/types.h>
 
-#include <boost/type_traits.hpp>
-
 #include <Eigen/Core>
 
+#include <boost/make_shared.hpp>
+#include <boost/utility/enable_if.hpp>
+
+
 namespace gtsam {
 
-  /**
-   * And our own `make_shared` as a layer of wrapping on `boost::make_shared`
-   */
+  /// Add our own `make_shared` as a layer of wrapping on `boost::make_shared`
   template<typename T, typename ... Args>
   boost::enable_if_t<has_custom_allocator<T>::value, boost::shared_ptr<T>> make_shared(Args&&... args)
   {
     return boost::allocate_shared<T>(Eigen::aligned_allocator<T>(), std::forward<Args> (args)...);
   }
 
+  /// Fall back to the boost version if no need for alignment
   template<typename T, typename ... Args>
   boost::enable_if_t<!has_custom_allocator<T>::value, boost::shared_ptr<T>> make_shared(Args&&... args)
   {