Add feed updated tag

Fixes #341

Author: steveklabnik

Cargo.lock

@@ -13,3 +13,4 @@ serde_json = "1.0"
 comrak = "0.4"
 fs_extra = "1.1.0"
 sass-rs = "0.2.1"
+time = "0.1.41"

Cargo.toml

@@ -237,7 +237,7 @@ impl Blog {
 
     fn render_feed(&self) -> Result<(), Box<Error>> {
         let posts: Vec<_> = self.posts.iter().by_ref().take(10).collect();
-        let data = json!({ "posts": posts });
+        let data = json!({ "posts": posts, "feed_updated":  time::now_utc().rfc3339().to_string() });
 
         self.render_template("feed.xml", "feed", data)?;
         Ok(())

src/main.rs

@@ -9,6 +9,7 @@
         <name>Maintained by the Rust Team.</name>
         <uri>https://github.com/rust-lang/blog.rust-lang.org/</uri>
     </author>
+    <updated>{{ feed_updated }}</updated>
 
     {{#each posts}}
     <entry>