Revert "Remove docs building from CI builds"

Now /docs is a Git subtree, so now this should just work.

This reverts commit 214dbdfb6f.

.travis.yml

@@ -15,6 +15,8 @@ install:
   - make vendor
 script:
   - make hugo-race check
+  - ./hugo -s docs/
+  - ./hugo --renderToMemory -s docs/
 before_install:
   # gem install must be run with sudo on OSX
   - sudo gem install asciidoctor | gem install asciidoctor

appveyor.yml

@@ -13,3 +13,5 @@ install:
 
 build_script:
   - make hugo-race check
+  - hugo -s docs/
+  - hugo --renderToMemory -s docs/