Add mappings for eks-1.0 and Kubernetes 1.18 (#654)

Allows user to specify either `--version` or `--benchmark-version` as `eks-1.0`
Allows user to specify (or auto-detect K8s version 1.18) and get the CIS 1.5 benchmark

cfg/config.yaml

@@ -196,6 +196,8 @@ version_mapping:
   "1.15": "cis-1.5"
   "1.16": "cis-1.5"
   "1.17": "cis-1.5"
+  "1.18": "cis-1.5"
+  "eks-1.0": "eks-1.0"
   "gke-1.0": "gke-1.0"
   "ocp-3.10": "rh-0.7"
   "ocp-3.11": "rh-0.7"