[checkstyle-tester] doc: Add min required Groovy runtime version in README.md
[checkstyle-tester] doc: Add min required Groovy runtime version in README.md
checkstyle/contribution,MEZk/contribution,Vladlis/contribution,rnveach/contribution,Vladlis/contribution,rnveach/contribution,checkstyle/contribution,rnveach/contribution,rnveach/contribution,Vladlis/contribution,checkstyle/contribution,checkstyle/contribution,MEZk/contribution,Vladlis/contribution,MEZk/contribution,MEZk/contribution,MEZk/contribution,rnveach/contribution,checkstyle/contribution,checkstyle/contribution,Vladlis/contribution,rnveach/contribution,MEZk/contribution,Vladlis/contribution,rnveach/contribution,checkstyle/contribution