Expand footer navigation mimicking the Bootstrap docs footer.

Adds

 * version information
 * links to the GitHub repository, issues and releases
 * links to the examples and options
 * a link to the 3.5.2 docs

to the footer as well as namespaced styles for the footer in general as well as all the above.

docs/_includes/footer.html

@@ -1,11 +1,19 @@
-<footer>
-  Select2 is licensed under the
-  <a href="https://github.com/select2/select2/blob/master/LICENSE.md">
-    MIT license.
-  </a>
-  The documentation is licensed under
-  <a href="https://creativecommons.org/licenses/by/3.0/">CC BY 3.0.</a>
-  Maintained by
-  <a href="https://github.com/kevin-brown">Kevin Brown</a> and
-  <a href="https://github.com/ivaynberg">Igor Vaynberg</a>.
+<footer class="s2-docs-footer" role="contentinfo">
+  <div class="container">
+    <p>
+      Select2 is licensed under <a href="https://github.com/select2/select2/blob/master/LICENSE.md">MIT</a>, documentation under <a href="https://creativecommons.org/licenses/by/3.0/">CC BY 3.0</a>.
+    </p>
+    <p>
+      Maintained by <a href="https://github.com/kevin-brown">Kevin Brown</a> and <a href="https://github.com/ivaynberg">Igor Vaynberg</a>.
+    </p>
+    <ul class="s2-docs-footer-links">
+      <li>Currently v4.0.0-rc.2</li>
+      <li><a href="https://github.com/select2/select2">GitHub</a></li>
+      <li><a href="./examples.html">Examples</a></li>
+      <li><a href="./options.html">Options</a></li>
+      <li><a href="http://select2.github.io/select2/">v3.5.2 docs</a></li>
+      <li><a href="https://github.com/select2/select2/issues">Issues</a></li>
+      <li><a href="https://github.com/select2/select2/releases">Releases</a></li>
+    </ul>
+  </div>
 </footer>

docs/_includes/head.html

@@ -21,8 +21,44 @@
 
 <style type="text/css">
   body { font-size: 16px; }
-  footer { background-color: #eee; margin-top: 1em; padding: 1em; text-align: center; }
+
+  /* Footer */
+  .s2-docs-footer {
+    border-top: 1px solid #E5E5E5;
+    color: #767676;
+    padding-top: 40px;
+    padding-bottom: 40px;
+    margin-top: 100px;
+    text-align: center;
+  }
+  .s2-docs-footer-links {
+    padding-left: 0;
+    margin-top: 20px;
+  }
+  .s2-docs-footer-links li {
+    display: inline;
+    padding: 0 2px;
+  }
+  .s2-docs-footer-links li:after {
+    content: "·";
+    padding-left: 8px;
+  }
+  .s2-docs-footer-links li:first-child {
+    padding-left: 0;
+  }
+  .s2-docs-footer-links li:last-child:after {
+    content: "";
+    padding-left: 0;
+  }
+  @media (min-width: 768px) {
+    .s2-docs-footer p {
+      margin-bottom: 0;
+    }
+  }
+
   .navbar-inverse .navbar-brand { color: #fff; }
+
+  /* anchor.js */
   .anchorjs-link {
     float: left;
     width: 1em;