change the travis-ci link in contribution section

README.md

@@ -105,4 +105,4 @@ Make sure the code meets following requirements before submitting your PR:
 
 Check following items after submitting the PR:
 
-- Compilations and unittests in [travis-ci](https://travis-ci.org/brpc/brpc) are passed.
\ No newline at end of file
+- Compilations and unittests in [travis-ci](https://travis-ci.org/brpc/brpc/pull_requests) are passed.

README_cn.md

@@ -106,4 +106,4 @@ brpc欢迎贡献代码，特别是对不同平台，协议的扩展代码。
 
 提交PR后请检查如下内容：
 
-* [travis-ci](https://travis-ci.org/brpc/brpc)中的编译和单测均已成功。
\ No newline at end of file
+* [travis-ci](https://travis-ci.org/brpc/brpc/pull_requests)中的编译和单测均已成功。