Feature/travis (#12)

* travis config

* Updated gemlock for htmlproofer.

* Note about installing nokogiri with bundle install.

* htmlproofer for cibuild

* Restricting the htmlproofer test to ignore /blog/

* Removed travis branch from the whitelist.

.travis.yml

@@ -0,0 +1,21 @@
+language: ruby
+rvm:
+- 2.3.1
+
+before_script:
+ - chmod +x ./script/cibuild # or do this locally and commit
+
+# Assume bundler is being used, therefore
+# the `install` step will run `bundle install` by default.
+script: ./script/cibuild
+
+# branch whitelist
+# branches:
+#   only:
+#   - feature/travis     # test the travis branch
+
+env:
+  global:
+  - NOKOGIRI_USE_SYSTEM_LIBRARIES=true # speeds up installation of html-proofer
+
+sudo: false # route your build to the container-based infrastructure for a faster build