Refactor + add more tests (Part 1) (#847)

* Refactor mdToHtml out

* Refactor routing + move it to server instead of core

* Refactor & Add more tests for server utils

* Refactor isSeparateCss function from server & generate

* Refactor insertTableOfContents from server & generate + add tests

* undo small nits

lib/server/routing.js

@@ -0,0 +1,46 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+function blog(baseUrl) {
+  return new RegExp(`^${baseUrl}blog/.*html$`);
+}
+
+function docs(baseUrl) {
+  return new RegExp(`^${baseUrl}docs/.*html$`);
+}
+
+function dotfiles() {
+  return /(?!.*html$)^\/.*\.[^\n/]+$/;
+}
+
+function feed(baseUrl) {
+  return new RegExp(`^${baseUrl}blog/(feed.xml|atom.xml)$`);
+}
+
+function noExtension() {
+  return /\/[^.]*\/?$/;
+}
+
+function page(baseUrl) {
+  const gr = regex => regex.toString().replace(/(^\/|\/$)/gm, '');
+  return new RegExp(
+    `(?!${gr(docs(baseUrl))}|${gr(blog(baseUrl))})^${baseUrl}.*.html$`
+  );
+}
+
+function sitemap(baseUrl) {
+  return new RegExp(`^${baseUrl}sitemap.xml$`);
+}
+
+module.exports = {
+  blog,
+  docs,
+  dotfiles,
+  feed,
+  page,
+  noExtension,
+  sitemap,
+};