Official abbreviations

Would be a better choice to use official abbreviations for cantons names.
Really difficult to use "litteral names" in Switzerland. For example: "Waadt" is writter in German but "Vaud" is the french name of this french speaking canton. "Bern" is in German, but "Berne" is the french name of this *bilingual* canton.

Ref: Official swiss admin website: http://www.bfs.admin.ch/bfs/portal/fr/index/dienstleistungen/premiere_visite/03/03_02.html

pygal/graph/swissmap.py

@@ -28,32 +28,32 @@ import os
 
 
 CANTONS = {
-    'kt-zh': u("Zürich"),
-    'kt-be': u("Bern"),
-    'kt-lu': u("Luzern"),
-    'kt-ju': u("Jura"),
-    'kt-ur': u("Uri"),
-    'kt-sz': u("Schwyz"),
-    'kt-ow': u("Obwalden"),
-    'kt-nw': u("Nidwalden"),
-    'kt-gl': u("Glarus"),
-    'kt-zg': u("Zug"),
-    'kt-fr': u("Freiburg"),
-    'kt-so': u("Solothurn"),
-    'kt-bl': u("Basel-Stadt"),
-    'kt-bs': u("Basle-Land"),
-    'kt-sh': u("Schaffhausen"),
-    'kt-ar': u("Appenzell Ausseroden"),
-    'kt-ai': u("Appenzell Innerroden"),
-    'kt-sg': u("St. Gallen"),
-    'kt-gr': u("Graubünden"),
-    'kt-ag': u("Aargau"),
-    'kt-tg': u("Thurgau"),
-    'kt-ti': u("Tessin"),
-    'kt-vd': u("Waadt"),
-    'kt-vs': u("Wallis"),
-    'kt-ne': u("Neuenburg"),
-    'kt-ge': u("Genf"),
+    'kt-zh': u("ZH"),
+    'kt-be': u("BE"),
+    'kt-lu': u("LU"),
+    'kt-ju': u("JH"),
+    'kt-ur': u("UR"),
+    'kt-sz': u("SZ"),
+    'kt-ow': u("OW"),
+    'kt-nw': u("NW"),
+    'kt-gl': u("GL"),
+    'kt-zg': u("ZG"),
+    'kt-fr': u("FR"),
+    'kt-so': u("SO"),
+    'kt-bl': u("BS"),
+    'kt-bs': u("BL"),
+    'kt-sh': u("SH"),
+    'kt-ar': u("AR"),
+    'kt-ai': u("AI"),
+    'kt-sg': u("SG"),
+    'kt-gr': u("GR"),
+    'kt-ag': u("AG"),
+    'kt-tg': u("TG"),
+    'kt-ti': u("TI"),
+    'kt-vd': u("VD"),
+    'kt-vs': u("VS"),
+    'kt-ne': u("NE"),
+    'kt-ge': u("GE"),
 }