Adding GitHub link to the navbar.

Author: jshbrntt

src/app/shared/navbar/navbar.html

@@ -8,5 +8,10 @@
   </a>
   <a md-button routerLink="components">Components</a>
   <a md-button routerLink="guides">Guides</a>
+  <a md-button class="pull-right" href="https://github.com/angular/material2" aria-label="GitHub Repository">
+    <img class="docs-github-logo"
+         src="../../../assets/img/homepage/github-circle-white-transparent.svg"
+         alt="GitHub">
+    <span>GitHub</span>
+  </a>
 </nav>
-

src/app/shared/navbar/navbar.scss

@@ -7,3 +7,9 @@
   height: 26px;
   vertical-align: middle;
 }
+
+.docs-github-logo {
+  margin: 0 7px 2px 0;
+  height: 21px;
+  vertical-align: middle;
+}