Add comment about pycha

tryton/gui/window/view_form/view/graph_gtk/bar.py

@@ -1,4 +1,5 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of this repository contains the full copyright notices and license terms.
+#This code is inspired by the pycha project (http://www.lorenzogil.com/projects/pycha/)
 from graph import Graph
 from tryton.common import hex2rgb, lighten
 import locale

tryton/gui/window/view_form/view/graph_gtk/graph.py

@@ -1,4 +1,5 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of this repository contains the full copyright notices and license terms.
+#This code is inspired by the pycha project (http://www.lorenzogil.com/projects/pycha/)
 import gtk
 from tryton.common import hex2rgb, generateColorscheme, DT_FORMAT, \
         COLOR_SCHEMES

tryton/gui/window/view_form/view/graph_gtk/line.py

@@ -1,4 +1,5 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of this repository contains the full copyright notices and license terms.
+#This code is inspired by the pycha project (http://www.lorenzogil.com/projects/pycha/)
 from graph import Graph
 from tryton.common import hex2rgb
 import locale

tryton/gui/window/view_form/view/graph_gtk/pie.py

@@ -1,4 +1,5 @@
 #This file is part of Tryton.  The COPYRIGHT file at the top level of this repository contains the full copyright notices and license terms.
+#This code is inspired by the pycha project (http://www.lorenzogil.com/projects/pycha/)
 from graph import Graph, Area
 import math
 import cairo