Make route path data available in vanilla context

Test Plan:
Ensure that `require("./src/app/routeData")` works in `node` without any
preprocessing. Ensure that `yarn start` works, and that `yarn build`
then `node ./bin/sourcecred.js start` also works.

wchargin-branch: vanilla-route-data

src/app/App.js

@@ -3,7 +3,8 @@
 import React from "react";
 import {Router, browserHistory} from "react-router";
 
-import {createRoutes, resolveTitleFromPath} from "./routes";
+import {createRoutes} from "./createRoutes";
+import {resolveTitleFromPath} from "./routeData";
 
 export default class App extends React.Component<{}> {
   render() {

src/app/Page.js

@@ -3,7 +3,7 @@
 import React, {type Node} from "react";
 import {Link} from "react-router";
 
-import {routeData} from "./routes";
+import {routeData} from "./routeData";
 import * as NullUtil from "../util/null";
 
 export default class Page extends React.Component<{|+children: Node|}> {

src/app/createRoutes.js

@@ -0,0 +1,21 @@
+// @flow
+
+import React from "react";
+import {IndexRoute, Route} from "react-router";
+
+import Page from "./Page";
+import {routeData} from "./routeData";
+
+export function createRoutes() {
+  return (
+    <Route path="/" component={Page}>
+      {routeData.map(({path, component}) => {
+        if (path === "/") {
+          return <IndexRoute key={path} component={component()} />;
+        } else {
+          return <Route key={path} path={path} component={component()} />;
+        }
+      })}
+    </Route>
+  );
+}

src/app/routeData.js

@@ -0,0 +1,49 @@
+// @flow
+
+// NOTE: This module must be written in vanilla ECMAScript that can be
+// run by Node without a preprocessor. That means that we use `exports`
+// and `require` instead of ECMAScript module keywords, we lazy-load all
+// dependent modules, and we use the Flow comment syntax instead of the
+// inline syntax.
+
+/*::
+type RouteDatum = {|
+  +path: string,
+  +component: () => React$ComponentType<{||}>,
+  +title: string,
+  +navTitle: ?string,
+|};
+*/
+
+const routeData /*: $ReadOnlyArray<RouteDatum> */ = [
+  {
+    path: "/",
+    component: () => require("./HomePage").default,
+    title: "SourceCred",
+    navTitle: "Home",
+  },
+  {
+    path: "/explorer",
+    component: () => require("./credExplorer/App").default,
+    title: "SourceCred explorer",
+    navTitle: "Explorer",
+  },
+];
+exports.routeData = routeData;
+
+function resolveRouteFromPath(path /*: string */) /*: ?RouteDatum */ {
+  const matches = (candidateRoute) => {
+    const candidatePath = candidateRoute.path;
+    const start = path.substring(0, candidatePath.length);
+    const end = path.substring(candidatePath.length);
+    return start === candidatePath && (end.length === 0 || end === "/");
+  };
+  return routeData.filter(matches)[0] || null;
+}
+
+function resolveTitleFromPath(path /*: string */) /*: string */ {
+  const route = resolveRouteFromPath(path);
+  const fallback = "SourceCred";
+  return route ? route.title : fallback;
+}
+exports.resolveTitleFromPath = resolveTitleFromPath;

src/app/routes.js

@@ -1,58 +0,0 @@
-// @flow
-
-import React from "react";
-import {IndexRoute, Route} from "react-router";
-
-import Page from "./Page";
-
-type RouteDatum = {|
-  +path: string,
-  +component: React$ComponentType<{||}>,
-  +title: string,
-  +navTitle: ?string,
-|};
-
-export const routeData: $ReadOnlyArray<RouteDatum> = [
-  {
-    path: "/",
-    component: require("./HomePage").default,
-    title: "SourceCred",
-    navTitle: "Home",
-  },
-  {
-    path: "/explorer",
-    component: require("./credExplorer/App").default,
-    title: "SourceCred explorer",
-    navTitle: "Explorer",
-  },
-];
-
-export function createRoutes() {
-  return (
-    <Route path="/" component={Page}>
-      {routeData.map(({path, component}) => {
-        if (path === "/") {
-          return <IndexRoute key={path} component={component} />;
-        } else {
-          return <Route key={path} path={path} component={component} />;
-        }
-      })}
-    </Route>
-  );
-}
-
-function resolveRouteFromPath(path: string): ?RouteDatum {
-  const matches = (candidateRoute) => {
-    const candidatePath = candidateRoute.path;
-    const start = path.substring(0, candidatePath.length);
-    const end = path.substring(candidatePath.length);
-    return start === candidatePath && (end.length === 0 || end === "/");
-  };
-  return routeData.filter(matches)[0] || null;
-}
-
-export function resolveTitleFromPath(path: string): string {
-  const route = resolveRouteFromPath(path);
-  const fallback = "SourceCred";
-  return route ? route.title : fallback;
-}

src/app/server.js

@@ -5,7 +5,8 @@ import React from "react";
 import ReactDOMServer from "react-dom/server";
 import {match, RouterContext} from "react-router";
 
-import {createRoutes, resolveTitleFromPath} from "./routes";
+import {createRoutes} from "./createRoutes";
+import {resolveTitleFromPath} from "./routeData";
 import dedent from "./dedent";
 
 export default function render(