Fixed broken "Getting Started" link on the front page

Author: jBugman

app/templates/index.hbs

@@ -7,7 +7,7 @@
             Install Cargo
         {{/link-to}}
 
-        <a href='https://doc.rust-lang.org/cargo/guide.html' class='yellow-button'>
+        <a href='https://doc.rust-lang.org/cargo/guide/' class='yellow-button'>
             {{svg-jar "flag"}}
             Getting Started
         </a>