add travis status

Author: Todd Berman

README.md

@@ -1,10 +1,10 @@
 # graphql-rxjava
 
-#### Friendly warning: As GraphQL itself is currently a Working Draft, expect changes.
-
 This is an execution strategy for [graphql-java](https://github.com/andimarek/graphql-java) that makes
 it easier to use rxjava's Observable.
 
+[![Build Status](https://travis-ci.org/nfl/graphql-rxjava.svg)](https://travis-ci.org/nfl/graphql-rxjava)
+
 # Table of Contents
 
 - [Rx Hello World](#hello-world)