improve dns explanation

docs/installation/_dns_config.rst

-Stackspin secures your connections with https certificates from `Let's Encrypt
-<https://letsencrypt.org>`__. In order to do this, DNS entries need to be
-created before you start the installation.
+Stackspin needs two DNS records that point to your cluster.  It is important to
+create these DNS records before you start the installation, so Stackspin can
+secure your connections with https certificates from `Let's Encrypt
+<https://letsencrypt.org>`__.
 
-Stackspin needs two DNS records that point to your cluster. Create these two DNS
-records:
+Create these two DNS records:
 
 -  An ``A`` record ``stackspin.example.org`` pointing to the cluster's IP address,
 -  A ``CNAME`` record ``*.stackspin.example.org`` pointing to ``stackspin.example.org``.
 
 .. Note::
 
-   It is also possible to host Stackspin on a domain (with
-   no dedicated subdomain). That does imply that the included WordPress site
-   will be hosted on your root domain ``example.org``. In that case, make these
-   DNS records instead:
+   It is also possible to host Stackspin on a domain without a dedicated
+   subdomain. That does imply that the included WordPress site will be hosted on
+   your root domain (i.e. ``https://example.org``). In that case, make these DNS
+   records instead:
 
-   - An ``A`` record ``example.org`` pointing to the VPS's IP address,
+   - An ``A`` record ``example.org`` pointing to the cluster's IP address,
    - A ``CNAME`` record ``*.example.org`` pointing to ``example.org``.