make Konva modular

test/import-test.js

@@ -0,0 +1,20 @@
+function equal(val1, val2, message) {
+  if (val1 !== val2) {
+    throw new Error('Not passed: ' + message);
+  }
+}
+
+// try to import only core
+let Konva = require('../lib/Core');
+
+// no external shapes
+equal(Konva.Rect, undefined, 'no external shapes');
+
+let Rect = require('../lib/shapes/Rect').Rect;
+
+equal(Rect !== undefined, true, 'Rect is defined');
+
+// now import from package.json
+let NewKonva = require('../');
+
+equal(NewKonva.Rect, Rect, 'Same rects');