Update Hugo test versions

Author: EmielH

.travis.yml

@@ -6,6 +6,8 @@ env:
   - HUGO_VERSION="0.54.0"
   - HUGO_VERSION="0.55.6"
   - HUGO_VERSION="0.56.3"
+  - HUGO_VERSION="0.57.2"
+  - HUGO_VERSION="0.58.3"
 
 install:
   - wget https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_${HUGO_VERSION}_Linux-64bit.tar.gz