add travis

Author: petertseng

.travis.yml

@@ -0,0 +1 @@
+travis.yml

README.md

@@ -1,5 +1,7 @@
 # adventofcode-rb-2016
 
+[![Build Status](https://travis-ci.org/petertseng/adventofcode-rb-2016.svg?branch=master)](https://travis-ci.org/petertseng/adventofcode-rb-2016)
+
 I'm reluctantly doing [Advent of Code](http://adventofcode.com) again.
 
 I say "reluctantly" because I got dragged into it by a friend midway through last year, and felt the need to follow through.

travis.yml

@@ -0,0 +1,18 @@
+language: ruby
+rvm:
+  - '2.4'
+  - '2.3'
+matrix:
+  allow_failures:
+    - rvm: '2.3'
+script: |
+  bad=""
+  for f in *.rb; do
+    if ! ruby -c $f; then
+      bad="$bad $f"
+    fi
+  done
+  if [ -n "$bad" ]; then
+    echo "bad: $bad"
+    exit 1
+  fi