Unify slugify()

Provides a new util.js file with a unified `slugify()` function that also
lowercases the slug. Change all uses of `slugify()` to use this instead.

src/util.js

@@ -0,0 +1,9 @@
+import baseSlugify from 'slugify';
+
+
+function slugify(s) {
+  // Slugify a string to our specs. Hooray consistency!
+  return baseSlugify(s).toLowerCase();
+}
+
+export { slugify };