remove beta support for sankey diagram

demos/sankey.html

@@ -20,12 +20,14 @@
           width: 800
           nodeAlignment: left
       ---
-      sankey-beta
-        Revenue,Expenses,10
-        Revenue,Profit,10
-        Expenses,Manufacturing,5
-        Expenses,Tax,3
-        Expenses,Research,2
+     sankey   
+        a,b,8
+        b,c,8
+        c,d,8
+        d,e,8
+        
+        x,c,4
+        c,y,4 
     </pre>
 
     <h2>Energy flow</h2>
@@ -40,7 +42,7 @@
           linkColor: gradient
           nodeAlignment: justify
       ---
-      sankey-beta
+      sankey
 
       Agricultural 'waste',Bio-conversion,124.729
       Bio-conversion,Liquid,0.597