Add smart ptr typedefs (#153)

urdf/include/urdf/model.h

@@ -41,6 +41,8 @@
 #include <map>
 #include <urdf_model/model.h>
 #include <tinyxml.h>
+#include <boost/shared_ptr.hpp>
+#include <boost/weak_ptr.hpp>
 
 namespace urdf{
 
@@ -59,6 +61,10 @@ public:
   bool initString(const std::string& xmlstring);
 };
 
+typedef boost::shared_ptr<Model> ModelSharedPtr;
+typedef boost::shared_ptr<const Model> ModelConstSharedPtr;
+typedef boost::weak_ptr<Model> ModelWeakPtr;
+
 }
 
 #endif