adding travis yml to test there as well

Author: vsoch

.travis.yml

@@ -0,0 +1,11 @@
+language: ruby
+rvm:
+- 2.3.1
+install:
+- bundle exec jekyll build
+script:
+- bundle exec jekyll build --trace
+- bundle exec htmlproofer ./_site --only-4xx --allow-hash-href
+env:
+  global:
+  - NOKOGIRI_USE_SYSTEM_LIBRARIES=true