Put NonlinearISAM into the gtsam namespace

gtsam/nonlinear/NonlinearISAM.h

@@ -23,6 +23,7 @@
 #include <gtsam/nonlinear/NonlinearFactorGraph.h>
 #include <gtsam/linear/GaussianISAM.h>
 
+namespace gtsam {
 /**
  * Wrapper class to manage ISAM in a nonlinear context
  */
@@ -82,3 +83,5 @@ public:
 	int reorderInterval() const { return reorderInterval_; }
 	int reorderCounter() const { return reorderCounter_; }
 };
+
+} // \namespace gtsam