Make `git submodule` invocation in README work. (#65)

diff --git a/README.md b/README.md
index c69af40..f40015a 100644
--- a/README.md
+++ b/README.md
@@ -5,7 +5,7 @@
 and Compression Data Format.
 
 You will need to first synchronize gflags and gtest by running
-`git submodule init --update --recursive`.
+`git submodule update --init --recursive`.
 
 A library with a simple API is included, as well as a command-line executable
 that can apply the encoder and decoder to source, target, and delta files.