Upgrade Hugo to 0.52 (#11552)

* Update Hugo version and apply HTML minification to production builds

* Use full flag names for clarity

* Remove Hugo installation logic out of Travis config and into Makefile

* Add Hugo version checking script

* Fix Netlify config version

.travis.yml

@@ -2,9 +2,6 @@ language: go
 go:
   - 1.10.2
 
-env:
-  - HUGO_VERSION=0.49
-
 jobs:
   include:
     - name: "Testing examples"
@@ -26,9 +23,6 @@ jobs:
       - go test -v k8s.io/website/content/en/examples
     - name: "Hugo build"
       install:
-      - curl -L https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_${HUGO_VERSION}_linux-64bit.tar.gz | tar -xz
-      - mkdir -p ${TRAVIS_HOME}/bin
-      - mv hugo ${TRAVIS_HOME}/bin
-      - export PATH=${TRAVIS_HOME}/bin:$PATH
+      - make travis-hugo-build
       script:
       - hugo