Fixed new pixel creation bug and preview canvas blurriness

It's now possible to create a new project of a different size from the one decided when opening the app. Also fixed a bug that made the layer preview canvases blurry. They're now pixel perfect.

css/pixel-editor.scss

@@ -22,6 +22,17 @@ body {
   /* Disable Android and iOS callouts*/
 }
 
+.preview-canvas {
+  image-rendering:optimizeSpeed;             /* Legal fallback */
+  image-rendering:-moz-crisp-edges;          /* Firefox        */
+  image-rendering:-o-crisp-edges;            /* Opera          */
+  image-rendering:-webkit-optimize-contrast; /* Safari         */
+  image-rendering:optimize-contrast;         /* CSS3 Proposed  */
+  image-rendering:crisp-edges;               /* CSS4 Proposed  */
+  image-rendering:pixelated;                 /* CSS4 Proposed  */
+  -ms-interpolation-mode:nearest-neighbor;   /* IE8+           */
+}
+
 #layers-menu {
   width:200px;
   top: 48px;