Tutorial improvements

web/tutorials/04-compilers.markdown

@@ -115,8 +115,10 @@ you to use:
 - `$path$` for the original filepath of the page;
 - `$foo$` where foo is specified in the metadata.
 
-`$date$` is not provided by default, you can see how we add it in the definition
-of `postCtx` in `site.hs`:
+`$date$` is not provided by default. In the scaffold, we use the convenience
+context function `dateField`, which will parse an `Item`'s filename to check if
+it begins with a date. You can see how we add it in the definition of `postCtx`
+in `site.hs`:
 
 ```haskell
 postCtx :: Context String

web/tutorials/external-add-tags-to-your-hakyll-blog.md

@@ -0,0 +1,6 @@
+---
+title: Add tags to your Hakyll blog
+author: Javran Cheng
+url: https://javran.github.io/posts/2014-03-01-add-tags-to-your-hakyll-blog.html
+external: true
+---

web/tutorials/external-deploying-with-widely.md

@@ -0,0 +1,6 @@
+---
+title: Deploying with Widely
+author: Kyle Marek-Spartz
+url: http://kyle.marek-spartz.org/posts/2013-12-09-widely-and-hakyll.html
+external: true
+---

web/tutorials/external-inlining-and-compressing-css.md

@@ -0,0 +1,6 @@
+---
+title: Inlining and compressing CSS
+author: Kyle Marek-Spartz
+url: http://kyle.marek-spartz.org/posts/2014-12-09-hakyll-css-template-compiler.html
+external: true
+---