docs: replace old used-by links in

fixes #187

Author: bryanbraun

docs/index.html

@@ -105,7 +105,7 @@ <h2 class="used-by-label">Used by</h2>
           width="96"
           height="96">
       </a>
-      <a href="https://middlemanapp.com/basics/install/">
+      <a href="https://middlemanapp.com/basics/start-new-site/">
         <img srcset="https://avatars1.githubusercontent.com/u/1280820?v=3&s=96,
                      https://avatars1.githubusercontent.com/u/1280820?v=3&s=192 2x"
           src="https://avatars1.githubusercontent.com/u/1280820?v=3&s=96"
@@ -125,7 +125,7 @@ <h2 class="used-by-label">Used by</h2>
           width="96"
           height="96">
       </a>
-      <a href="https://bundler.io/v1.15/guides/deploying.html">
+      <a href="https://bundler.io/guides/faq.html">
         <img srcset="https://avatars1.githubusercontent.com/u/1137638?v=3&s=96,
                      https://avatars1.githubusercontent.com/u/1137638?v=3&s=192 2x"
           src="https://avatars1.githubusercontent.com/u/1137638?v=3&s=96"