Set up sampleOrder with the correct types

Author: mindgraffiti

Yosemite/YosemiteTests/Stores/OrderStoreTests.swift

@@ -104,8 +104,8 @@ private extension OrderStoreTests {
                      status: .processing,
                      currency: "USD",
                      customerNote: "",
-                     dateCreated: date(with: "2018-04-03T23:05:12"),
-                     dateModified: date(with: "2018-04-03T23:05:14"),
+                     dateCreatedString: "2018-04-03T23:05:12",
+                     dateModifiedString: "2018-04-03T23:05:14",
                      datePaid: date(with: "2018-04-03T23:05:14"),
                      discountTotal: "30.00",
                      discountTax: "1.20",