cfssljson now has -version flag

docs/02-client-tools.md

@@ -60,7 +60,19 @@ Revision: dev
 Runtime: go1.6
 ```
 
-> The cfssljson command line utility does not provide a way to print its version.
+Verify `cfssljson` version 1.2.0 or higher is installed:
+
+```
+cfssljson -version
+```
+
+> output
+
+```
+Version: 1.2.0
+Revision: dev
+Runtime: go1.9.2
+```
 
 ## Install kubectl