add travis support

pkgs/markdown/.travis.yml

diff --git a/pkgs/markdown/.travis.yml b/pkgs/markdown/.travis.yml
new file mode 100644
index 0000000..02adae0
--- /dev/null
+++ b/pkgs/markdown/.travis.yml
@@ -0,0 +1,5 @@
+language: dart
+sudo: false
+dart:
+  - stable
+  - dev

pkgs/markdown/README.md

diff --git a/pkgs/markdown/README.md b/pkgs/markdown/README.md
index fcd27eb..adab618 100644
--- a/pkgs/markdown/README.md
+++ b/pkgs/markdown/README.md
@@ -1,3 +1,5 @@
+[![Build Status](https://travis-ci.org/dart-lang/markdown.svg?branch=master)](https://travis-ci.org/dart-lang/markdown)
+
 A portable Markdown library written in Dart. It can parse Markdown into
 HTML on both the client and server.