add a Travis build

this should be useful for lightly sanity-checking pull requests --
at least we'll know if it stops the site from generating

Author: SethTisue

.travis.yml

@@ -0,0 +1,13 @@
+# opt-in to Travis new infrastructure
+sudo: false
+
+language: ruby
+
+# we must override install, or Travis's default Gemfile support
+# will kick in and use `vendor`, ignoring our BUNDLE_PATH
+# declaration in `.bundle/config`
+install:
+- bundle install
+
+script:
+- bundle exec jekyll build