Issue #631 Add a note about cert expire time limit to readme.

We have detail about it in the doc troubleshoot section but not
in the readme, better to have it here also.

README.adoc

@@ -4,6 +4,20 @@
 :toc-title:
 :toclevels:
 
+[NOTE]
+====
+Each released `crc` binary expires 30 days after the release due to certificates embedded in the Openshift cluster.
+Using an older `crc` binary will result in an expired certificates error.
+
+To resolve this error:
+
+* link:https://github.com/code-ready/crc/releases[Download the latest CodeReady Containers release] and place the `crc` binary in your `$PATH`.
+* Remove the cluster with certificate errors using the `crc delete` command.
+* Set up the new release with the `crc setup` command.
+* Start the new cluster with the `crc start` command.
+
+====
+
 toc::[]
 
 image:https://travis-ci.org/code-ready/crc.svg?branch=master["Travis CI Build Status", link="https://travis-ci.org/code-ready/crc"]