Fix notebook kernel selection and auto-kernel-start (#254)

* Fix bug: cannot select kernel. Properly plug-in kernelspecs middleware to redux store configuration

* Properly auto-launch kernel with nteract's epic

* Keep kernel lazy start for notebook viewer

* Add unit tets

src/Explorer/Notebook/notebookClientV2.test.ts

@@ -0,0 +1,48 @@
+jest.mock("./NotebookComponent/store");
+jest.mock("@nteract/core");
+import { NotebookClientV2 } from "./NotebookClientV2";
+import configureStore from "./NotebookComponent/store";
+import { defineConfigOption } from "@nteract/mythic-configuration";
+
+describe("auto start kernel", () => {
+  it("configure autoStartKernelOnNotebookOpen properly depending whether notebook is/is not read-only", async () => {
+    (configureStore as jest.Mock).mockReturnValue({
+      dispatch: () => {
+        /* noop */
+      }
+    });
+
+    defineConfigOption({
+      label: "editorType",
+      key: "editorType",
+      defaultValue: "foo"
+    });
+
+    defineConfigOption({
+      label: "autoSaveInterval",
+      key: "autoSaveInterval",
+      defaultValue: 1234
+    });
+
+    [true, false].forEach(isReadOnly => {
+      new NotebookClientV2({
+        connectionInfo: {
+          authToken: "autToken",
+          notebookServerEndpoint: "notebookServerEndpoint"
+        },
+        databaseAccountName: undefined,
+        defaultExperience: undefined,
+        isReadOnly,
+        contentProvider: undefined
+      });
+
+      expect(configureStore).toHaveBeenCalledWith(
+        expect.anything(), // initial state
+        undefined, // content provider
+        expect.anything(), // onTraceFailure
+        expect.anything(), // customMiddlewares
+        !isReadOnly
+      );
+    });
+  });
+});