Introduce new Markdown shortcuts, revisit old blog posts

This does a number of things:
- Introduces new shortcodes for figures and tables, allowing them
  to be embedded natively.
- Fixes padding on Youtube videos
- Adjusts old blog posts, fixing dead links, and updating/unifying
  syntax.

gulpfile.js

@@ -150,6 +150,7 @@ gulp.task('final:serve', function() {
     gulp.watch('src/js/**/*', ['assets:js']);
     gulp.watch('src/scss/**/*', ['assets:scss']);
     gulp.watch('site/**/*.html', ['hugo']);
+    gulp.watch('site/**/*.md', ['hugo']);
 
     gulp.watch('build/**/*').on('change', fileChange);
 });