Reorganizing Customizing the Build

Topic reorg to highlight important stuff

with @MariadeAnton

Author: plaindocs

_includes/sidebar.html

@@ -31,10 +31,8 @@
       <h3>Getting Started</h3>
       <ul>
         <li><a href="/user/getting-started/">Getting started</a></li>
-        <li><a href="/user/customizing-the-build/">Customizing Your Build</a></li>
-        <li><a href="/user/common-build-problems/">Common Build Problems</a></li>
+        <li><a href="/usercommon-build-problems/">Common Build Problems</a></li>
         <li><a href="/user/speeding-up-the-build/">Speeding up the Build</a></li>
-        <li><a href="/user/build-stages/">Build Stages (beta)</a></li>
         <li><a href="/user/docker/">Using Docker in your Build</a></li>
         <li><a href="/user/gui-and-headless-browsers/">Headless Testing with Browsers</a></li>
         <li><a href="/user/pull-requests/">Building Pull Requests</a></li>
@@ -43,15 +41,25 @@ <h3>Getting Started</h3>
         <li><a href="https://github.com/travis-ci/travis#readme">Command Line Client</a></li>
         <li><a href="/user/travis-lint/">Validating .travis.yml files</a></li>
       </ul>
-
+      <h3>Customizing the Build</h3>
+      <ul>
+        <li><a href="/user/customising-the-build/build-lifecycle/">The Build Lifecycle</a></li>
+        <li><a href="/user/customising-the-build/build-stages/">Build Stages (beta)</a></li>
+        <li><a href="/user/customising-the-build/build-matrix/">Build Matrix</a></li>
+        <li><a href="/user/customising-thebuild/limiting-concurrent-builds/">Limiting Concurrent Builds</a></li>
+        <li><a href="/user/customising-thebuild/building-only-the-latest-commit/">Building only the latest commit</a></li>
+        <li><a href="/user/customising-thebuild/building-specific-branches/">Building Specific Branches</a></li>
+        <li><a href="/user/customising-thebuild/second-Programming-language/">Using a Second Programming language</a></li>
+        <li><a href="/user/customising-thebuild/skipping-a-build/">Skipping a build</a></li>
+        <li><a href="/user/customizing-the-build/further-customization/">Further customization</a></li>
+      </ul>
       <h3>Installing Dependencies</h3>
       <ul>
         <li><a href="/user/installing-dependencies/">Installing Dependencies</a></li>
         <li><a href="/user/private-dependencies/">Private Dependencies</a></li>
         <li><a href="/user/database-setup/">Setting up Services and Databases</a></li>
         <li><a href="/user/caching/">Caching Dependencies</a></li>
         <li><a href="/user/ssh-known-hosts/">Adding to SSH Known Hosts</a></li>
-
       </ul>
       <h3>Programming Languages</h3>
       <ul>