Make it possible to delete all vertex edges at once.

src/data-structures/graph/GraphVertex.js

@@ -119,6 +119,15 @@ export default class GraphVertex {
     return this.value;
   }
 
+  /**
+   * @return {GraphVertex}
+   */
+  deleteAllEdges() {
+    this.getEdges().forEach(edge => this.deleteEdge(edge));
+
+    return this;
+  }
+
   /**
    * @param {function} [callback]
    * @returns {string}