Add drone.io build badge to README.md
diff --git a/README.md b/README.md
index a713aa9..9edee21 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,7 @@
 benchmark
 =========
+[![Build Status](https://drone.io/github.com/google/benchmark/status.png)](https://drone.io/github.com/google/benchmark/latest)
+
 A library to support the benchmarking of functions, similar to unit-tests.
 
 Example usage: