feat(seed): "unpack" and "repack" scripts

add "npm run seed" as alias to "node seed"

unpack tests and solution into HTML file; add titles and help text; style unpacked file

enable running unpacked assert tests in browser

Using browserify, compile "tape", "lodash", jQuery into "unpacked-bundle.js" for use during in-browser unpacked tests

feat(seed): diff after repacking

feat(seed): unpacked tests use Browser TAP chrome dev tool if available

mongoIds.js

@@ -0,0 +1,24 @@
+import _ from 'lodash';
+import { isMongoId } from 'validator';
+
+class MongoIds {
+  constructor() {
+    this.knownIds = [];
+  }
+  check(id, title) {
+    if (!isMongoId(id)) {
+      throw new Error(`Expected a valid ObjectId for ${title}, but got ${id}`);
+    }
+    const idIndex = _.findIndex(this.knownIds, existing => id === existing);
+    if (idIndex !== -1) {
+      throw new Error(`
+    All challenges must have a unique id.
+
+    The id for ${title} is already assigned
+    `);
+    }
+    this.knownIds = [ ...this.knownIds, id ];
+  }
+}
+
+export default MongoIds;