bug 567547 - use col-pull and remove the empty span

bug 567547 - align contact us button center on mobile view for resources tab

Signed-off-by: Yi Liu <yi.liu@eclipse-foundation.org>
Change-Id: I8ebb7a3c2cd80a6fb6c67f8221327f5833751849
diff --git a/content/en_index.php b/content/en_index.php
index 113b225..ee095a3 100644
--- a/content/en_index.php
+++ b/content/en_index.php
@@ -366,9 +366,8 @@
         
         <!-- Nav -->
         <div class="margin-top-40 vertical-align">
-          <a class="hidden-xs col-sm-6 col-md-8 text-left alt-tab-toggle" href="#tab-membership">&lt; How to become a member</a>
-          <a class="col-xs-22 col-sm-12 col-md-8 btn btn-primary" href="https://accounts.eclipse.org/contact/membership">Contact Us About Membership</a>
-          <span class="col-sm-6 col-md-8"></span>
+          <a class="hidden-xs col-sm-6 col-md-8 col-sm-pull-3 col-md-pull-4 text-left alt-tab-toggle" href="#tab-membership">&lt; How to become a member</a>
+          <a class="col-xs-22 col-sm-12 col-sm-pull-3 col-md-pull-4 col-md-8 btn btn-primary" href="https://accounts.eclipse.org/contact/membership">Contact Us About Membership</a>
         </div>
       </div>
     </div>