add Travis CI support

Author: SkypLabs

.travis.yml

@@ -0,0 +1,27 @@
+sudo: required
+
+language: ruby
+
+services:
+  - docker
+
+install: gem install html-proofer
+
+script: htmlproofer index.html
+
+env:
+  global:
+    - NOKOGIRI_USE_SYSTEM_LIBRARIES=true # speeds up installation of html-proofer
+
+before_deploy: docker run --rm -u $(id -u):$(id -g) -v $(pwd):/home astefanutti/decktape /home/index.html /home/Code_versioning_an_introduction_with_Git.pdf
+
+deploy:
+  provider: releases
+  api_key:
+    secure: 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
+  file: Code_versioning_an_introduction_with_Git.pdf
+  skip_cleanup: true
+  overwrite: true
+  on:
+    repo: SkypLabs/git-slideshow
+    tags: true