Add script/travis so all people can play with Travis-CI images.

script/travis

@@ -0,0 +1,36 @@
+#!/bin/sh
+# Usage: script/travis [ruby-version [file]]
+# Example: script/travis 2.0 test/failing_test.rb
+# Example: script/travis 2.3.0
+set -e
+
+mkdir -p vendor/docker
+docker rm -fv docker-travis > /dev/null 2>&1 || true
+docker run --volume=$(pwd):/home/travis/builds/jekyll/jekyll \
+  --workdir=/home/travis/builds/jekyll/jekyll \
+  --volume=$(pwd)/vendor/docker:/home/travis/builds/jekyll/jekyll/vendor/bundle \
+  --user=travis --name=docker-travis -dit quay.io/travisci/travis-ruby \
+      bash > /dev/null
+
+status=0
+if [ $# -eq 2 ]; then
+  docker exec -it docker-travis bash -ilc " \
+    rvm use --install --binary --fuzzy $1
+    bundle install --path vendor/bundle -j 256
+    script/test $2
+  " || status=$?
+
+elif [ $# -eq 1 ]; then
+  docker exec -it docker-travis bash -ilc " \
+    rvm use --install --binary --fuzzy $1
+    bundle install --path vendor/bundle -j 256
+    bundle exec rake
+  " || status=$?
+
+else
+  docker exec -it docker-travis \
+    bash -il || status=$?
+fi
+
+docker rm -fv docker-travis > /dev/null
+exit $status