adding missing setTransform method (#52)

Author: yilinwei

src/Graphics/Canvas.js

@@ -314,6 +314,15 @@ exports.transform = function(t) {
     };
 };
 
+exports.setTransform = function(t) {
+    return function(ctx) {
+        return function() {
+            ctx.setTransform(t.m11, t.m12, t.m21, t.m22, t.m31, t.m32);
+            return ctx;
+        };
+    };
+};
+
 exports.clearRect = function(ctx) {
     return function(r) {
         return function() {

src/Graphics/Canvas.purs

@@ -476,9 +476,12 @@ type Transform =
   , m32 :: Number
   }
 
--- | Apply a general transformation.
+-- | Apply a general transformation to the current transformation matrix
 foreign import transform :: forall eff. Transform -> Context2D -> Eff (canvas :: CANVAS | eff) Context2D
 
+-- | Set the transformation matrix
+foreign import setTransform :: forall eff. Transform -> Context2D -> Eff (canvas :: CANVAS | eff) Context2D
+
 -- | Enumerates types of text alignment.
 data TextAlign
   = AlignLeft | AlignRight | AlignCenter | AlignStart | AlignEnd