fix travis check style

paddle/scripts/travis/check_style.sh

 #!/bin/bash
 function abort(){
     echo "Your change doesn't follow PaddlePaddle's code style." 1>&2
-    echo "Please use pre-commit to reformat your code and git push again." 1>&2
+    echo "Please use pre-commit to check what is wrong." 1>&2
     exit 1
 }
 
@@ -19,7 +19,8 @@ ln -sf $TRAVIS_BUILD_DIR $GOPATH/src/github.com/PaddlePaddle/Paddle
 cd  $GOPATH/src/github.com/PaddlePaddle/Paddle/go; glide install; cd -
 
 if ! pre-commit run -a ; then
-  git diff  --exit-code
+    git diff
+    exit 1
 fi
 
 trap : 0