Make gitlab CI example script faster (#1171)

By using alpine, the time to pull and start the container decreases.
By using the official alpine zola package, the script gets simpler.
Also, this updates the zola version to the latest release.

docs/content/documentation/deployment/gitlab-pages.md

@@ -1,4 +1,4 @@
- +++
++++
 title = "GitLab Pages"
 weight = 40
 +++
@@ -37,20 +37,19 @@ The second step is to tell the GitLab continuous integration runner how to creat
 To do this, create a file called `.gitlab-ci.yml` in the root directory of your repository.
 
 ```yaml
+image: alpine:latest
 variables:
   # This variable will ensure that the CI runner pulls in your theme from the submodule
   GIT_SUBMODULE_STRATEGY: recursive  
   # Specify the zola version you want to use here
-  ZOLA_VERSION: "v0.9.0"
+  ZOLA_VERSION: "v0.12.0"
 
 pages:
   script:
-    # Download the zola executable and store it in zola.tar.gz
-    - curl -L https://github.com/getzola/zola/releases/download/$ZOLA_VERSION/zola-$ZOLA_VERSION-x86_64-unknown-linux-gnu.tar.gz > zola.tar.gz
-    # Unpack the zola executable
-    - tar -xzf zola.tar.gz
+    # Install the zola package from the alpine testing repositories
+    - apk add --update-cache --repository http://dl-3.alpinelinux.org/alpine/edge/testing/ zola
     # Execute zola build
-    - ./zola build
+    - zola build
     
   artifacts:
     paths:
@@ -58,8 +57,8 @@ pages:
       - public
       
   # This config will only publish changes that are pushed on the master branch
-  only:
-  - master
+  only: 
+    - master
 ```
 
 Push this new file and ... Tada! You're done! If you navigate to `settings > pages`, you should be able to see