Rational bezier (#208)

* .

* meh

* rational beziers

lib/site/handlers.js

@@ -342,6 +342,43 @@ window["Bezier Section Handlers"] = {
       });
     }
   }
+};
+ }())
+  },
+  "weightcontrol": {
+    handler: (function() { var ratios;
+
+return {
+  drawCubic: function(api) {
+    var curve = new api.Bezier(
+      120, 160,
+      35,  200,
+      220, 260,
+      220, 40
+    );
+    api.setCurve(curve);
+  },
+
+  drawCurve: function(api, curve) {
+    api.reset();
+    api.drawSkeleton(curve);
+    api.drawCurve(curve);
+  },
+
+  setRatio: function(api, values) {
+    ratios = values;
+    this.update(api);
+  },
+
+  changeRatio: function(api, value, pos) {
+    ratios[pos] = parseFloat(value) || 0.00001;
+    this.update(api);
+  },
+
+  update: function(api) {
+    api.curve.setRatios(ratios.slice());
+    this.drawCurve(api, api.curve);
+  }
 };
  }())
   },
@@ -626,6 +663,12 @@ var Reordering = {
     var Mt = transpose(M);
     var Mc = multiply(Mt, M);
     var Mi = invert(Mc);
+
+    if (!Mi) {
+      console.error('MtM has no inverse?');
+      return curve;
+    }
+
     var V = multiply(Mi, Mt);
 
     // And then we map our k-order list of coordinates