Add automated HTML tests (#70)

* Add gemfile lock to gitingore

Add a rule to the gitignore file to ignore the Gemfile.lock generated file.

* Add automated tests

Add automated tests of the website through Travis CI.

.gitignore

@@ -4,3 +4,4 @@ _site/
 node_modules/
 .jekyll-metadata
 *.patch
+Gemfile.lock

.travis.yml

@@ -0,0 +1,11 @@
+language: ruby
+rvm:
+  - 2.2
+sudo: false
+script:
+  - bundle exec jekyll build
+  - bundle exec htmlproofer '_site/' --allow-hash-href --check-html
+
+env:
+  global:
+    - NOKOGIRI_USE_SYSTEM_LIBRARIES=true # speeds up installation of html-proofer

Gemfile

@@ -0,0 +1,4 @@
+source 'https://rubygems.org'
+gem 'jekyll'
+gem 'jekyll-redirect-from'
+gem 'html-proofer'