Add travis (#2)

* Create .travis.yml

* Update README.md
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..850bb90
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,4 @@
+language: dart
+dart_task:
+- dartanalyzer
+- dartfmt
diff --git a/README.md b/README.md
index 14d569c..4045771 100644
--- a/README.md
+++ b/README.md
@@ -1,2 +1,4 @@
 # characters
+[![Build Status](https://travis-ci.org/dart-lang/characters.svg?branch=master)](https://travis-ci.org/dart-lang/characters)
+
 A package for characters represented as unicode extended grapheme clusters