Enable mod_rewrite in apache

Enable mod_rewrite in apache

`mod_rewrite` uses a rule-based rewriting engine (based on a regular-expression parser) to rewrite requested URLs on the fly.
To enable the rewrite module :
```
sudo a2enmod rewrite
```

You need to restart the webserver to apply the changes:
```
sudo service apache2 restart
```

If you plan on using mod_rewrite in `.htaccess` files, you also need to enable the use of `.htaccess` files by changing `AllowOverride None` to `AllowOverride FileInfo`. 
For the default website, edit `/etc/apache2/sites-available/default`:
```
<Directory /var/www/>
        Options Indexes FollowSymLinks MultiViews
        # changed from None to FileInfo
        AllowOverride FileInfo
        Order allow,deny
        allow from all
</Directory>
```

After such a change, you need to restart Apache again.