Updated sideloading link so we're not recommending AirDroid.

See http://arstechnica.co.uk/security/2016/12/at-least-10-million-android-users-imperiled-by-popular-airdroid-app/

building.html

@@ -79,7 +79,7 @@
 
           <img src="img/building/13.png">
 
-          <p>9) When the build process finishes, click <b>Show in File Manager</b> to open the folder containing the APK file, <b>briar-android-debug.apk</b>. You can <a href="http://www.greenbot.com/article/2452614/how-to-sideload-an-app-onto-your-android-phone-or-tablet.html">sideload</a> this file onto any Android device.</p>
+          <p>9) When the build process finishes, click <b>Show in File Manager</b> to open the folder containing the APK file, <b>briar-android-debug.apk</b>. You can <a href="http://www.digitalcitizen.life/how-sideload-apps-using-apk-files-android-devices">sideload</a> this file onto any Android device.</p>
 
           <img src="img/building/11.png">