name correct minimum inspec version

Signed-off-by: Christoph Hartmann <chris@lollyrock.com>

Author: chris-rock

README.md

@@ -12,7 +12,7 @@ InSpec is an open-source run-time framework and rule language used to specify co
 
 ## Requirements
 
-* at least [InSpec](http://inspec.io/) version 1.21.0
+* at least [InSpec](http://inspec.io/) version 1.38.8
 * Docker 1.13+
 
 ### Platform