Redirect www to naked domain

I'm trying to redirect all of my website traffic to my naked domain (looks much cleaner in my opinion), but when Googling I found a LOT of different methods for going about it. I use CloudFlare's free SSL, so I'd like a solution that works both with and without SSL (in case something happens and I disable the SSL or whatever), and I'd preferably like to do this globally (i.e. without a .htaccess file). In case it matters, this is Apache 2.4.10 on Ubuntu Server 14.10.

I found this article, but placing his code (below) into my VirtualHost directive gave the error that is below. The Apache error log doesn't have anything useful. What can I do to fix this problem and make it so the redirect works properly? (If I should be doing this some other way I'm open to that as well; I have access to control my DNS settings and whatnot if needed.)

Code inserted into apache2/sites-available/000-default.conf:

RewriteEngine on
RewriteCond %{HTTPS} off
RewriteCond %{HTTP_HOST} !^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://www.%{HTTP_HOST}/$1 [R=301,L]

RewriteCond %{HTTPS} on
RewriteCond %{HTTP_HOST} !^www\.(.*)$ [NC]
RewriteRule ^(.*)$ https://www.%{HTTP_HOST}/$1 [R=301,L]

Error code I receive when restarting Apache:

 * The apache2 configtest failed.
Output of config test was:
AH00526: Syntax error on line 30 of /etc/apache2/sites-enabled/000-default.conf:
Invalid command 'RewriteEngine', perhaps misspelled or defined by a module not included in the server configuration
Action 'configtest' failed.
The Apache error log may have more information.

Solution

The rewrite module is not enabled by default.

Enable the rewrite module:

sudo a2enmod rewrite

change your 000-default.conf to

RewriteCond %{HTTPS} on
RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
RewriteRule ^(.*)$ https://%1/$1 [R=301,L]

RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]

then
```
sudo service apache2 restart
```