README: Avoid duplicate implict target

Rename document title, so it does not duplicate with caucase section in
command line usage.

It seems the only solution as noted in https://stackoverflow.com/questions/4843052/how-to-deal-with-duplicate-target-names-in-restructuredtext

README.rst

-=======
-caucase
-=======
-
-Certificate Authority for Users, Certificate Authority for SErvices
+=============================================================================
+caucase - Certificate Authority for Users, Certificate Authority for SErvices
+=============================================================================
 
 Overview
 ========