update history

Author: mdeff

doc/history.rst

@@ -9,13 +9,19 @@ The plotting interface was updated to be more user-friendly. First, the
 documentation is now shown for filters.plot(), G.plot(), and co. Second, the
 API in the plotting library has been deprecated. That module is now mostly for
 implementation only. Finally, the following parameter names were changed:
+
 * plot_name => title
 * plot_eigenvalues => eigenvalues
 * show_sum => sum
 * show_edges => edges
 * npoints => n
 * save_as => save
 
+Additional features:
+
+* print(graph) and print(filters) now show valuable information.
+* Building a graph object is much faster.
+
 0.5.1 (2017-12-15)
 ------------------