add hook

.travis/precommit.sh

+#!/bin/bash
+function abort(){
+    echo "Your commit does not fit PaddlePaddle code style" 1>&2
+    echo "Please use pre-commit scripts to auto-format your code" 1>&2
+    exit 1
+}
+
+trap 'abort' 0
+set -e
+cd `dirname $0`
+cd ..
+export PATH=/usr/bin:$PATH
+pre-commit install
+
+if ! pre-commit run -a ; then
+  ls -lh
+  git diff  --exit-code
+  exit 1
+fi
+
+trap : 0