Make node counts attributes

• Also fix all usages

src/SparseTransform/DataStructures/AdjacencyGraph.cs

@@ -13,6 +13,17 @@ namespace SparseTransform.DataStructures
         /// </remarks>
         private List<GraphNode> _nodes;
 
+        /// <summary>
+        /// Number of nodes
+        /// </summary>
+        public int NodeCount
+        {
+            get
+            {
+                return _nodes.Count;
+            }
+        }
+
         private int _maxDegree = 0;
         /// <summary>
         /// Get the degree of the node with most neighbors.
@@ -117,15 +128,6 @@ namespace SparseTransform.DataStructures
             return nodes as IEnumerable<GraphNode>;
         }
 
-        /// <summary>
-        /// Get number of nodes
-        /// </summary>
-        /// <returns>number of nodes</returns>
-        public int GetNodeCount()
-        {
-            return _nodes.Count;
-        }
-
         /// <summary>
         /// Finds a node by index. Returns null if not found.
         /// </summary>