Add command for running unit tests to README.md

Change-Id: Iedb7afb9d9bae08453fda14e838ee908c64dbe2f

README.md

diff --git a/README.md b/README.md
index b5cdfe1..c5b4ff3 100644
--- a/README.md
+++ b/README.md
@@ -21,6 +21,7 @@
   cd /path/to/gitiles
   git submodule update --init
   buck build all
+  buck test
 ```
 
 
@@ -36,6 +37,8 @@
 http://localhost:8080/ to view your local copy of gitiles, which
 will serve any repositories under `/path/to/repositories`.
 
+To run unit tests, run `buck test`.
+
 
 Eclipse IDE
 -----------