start to refactor components.

lib/__tests__/product-test.ts

@@ -20,4 +20,11 @@ describe("Product tests", () => {
     const comparison = standard.priceFor({l : 24, u: "inch"});
     expect(comparison).toBeCloseTo(20, 4);
   });
+
+  it("Can convert to/from object", () => {
+    const standard = new Product(10, {l: 1, u : "feet"});
+    const obj = standard.asObject;
+    const back = Product.fromObject(obj);
+    expect(back).toEqual(standard);
+  })
 });