Fix branch name used in build status.

The README in the master branch should show the build status of
master branch.
diff --git a/README.md b/README.md
index 51b6569..1d0c4b9 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,7 @@
 
 |         |Android |Windows |OS X |Linux |NaCl |
 |---------|:------:|:------:|:---:|:----:|:---:|
-|**Build**|N/A     | N/A    |[![Build Status](https://travis-ci.org/google/mozc.svg?branch=travis-initial-setup)](https://travis-ci.org/google/mozc) |N/A |N/A |
+|**Build**|N/A     | N/A    |[![Build Status](https://travis-ci.org/google/mozc.svg?branch=master)](https://travis-ci.org/google/mozc) |N/A |N/A |
 
 
 What's Mozc?