add missing apt-get update line in readme, close #7

Author: fredszaq

README.md

@@ -27,6 +27,7 @@ Before runing these scripts, you need to have `bazel`
 ```
 $ echo "deb [arch=amd64] http://storage.googleapis.com/bazel-apt stable jdk1.8" | sudo tee /etc/apt/sources.list.d/bazel.list
 $ curl https://bazel.build/bazel-release.pub.gpg | sudo apt-key add -
+$ sudo apt-get update
 $ sudo apt-get install bazel
 ```