Merge branch 'develop' into mt

.pre-commit-config.yaml

+-   repo: https://github.com/Lucas-C/pre-commit-hooks.git
+    sha: c25201a00e6b0514370501050cf2a8538ac12270
+    hooks:
+    -   id: remove-crlf
+-   repo: https://github.com/reyoung/mirrors-yapf.git
+    sha: v0.13.2
+    hooks:
+    - id: yapf
+      files: (.*\.(py|bzl)|BUILD|.*\.BUILD|WORKSPACE)$  # Bazel BUILD files follow Python syntax.
+-   repo: https://github.com/pre-commit/pre-commit-hooks
+    sha: 7539d8bd1a00a3c1bfd34cdb606d3a6372e83469
+    hooks:
+    -   id: check-added-large-files
+    -   id: check-merge-conflict
+    -   id: check-symlinks
+    -   id: detect-private-key
+    -   id: end-of-file-fixer

.style.yapf

+[style]
+based_on_style = pep8
+column_limit = 80

.travis.yml

+language: cpp
+cache: ccache
+sudo: required
+dist: trusty
+os:
+  - linux
+env:
+  - JOB=PRE_COMMIT
+
+addons:
+  apt:
+    packages:
+      - git
+      - python
+      - python-pip
+      - python2.7-dev
+before_install:
+  -  pip install virtualenv pre-commit
+script:
+  - travis/precommit.sh
+notifications:
+  email:
+    on_success: change
+    on_failure: always

README.md

 # 深度学习入门
 
 1. [新手入门](fit_a_line/README.md)
-1. [个性化推荐](recommender_system/README.md)
 1. [识别数字](recognize_digits/README.md)
 1. [图像分类](image_classification/README.md)
 1. [词向量](word2vec/README.md)
 1. [情感分析](understand_sentiment/README.md)
 1. [文本序列标注](label_semantic_roles/README.md)
 1. [机器翻译](machine_translation/README.md)
+1. [个性化推荐](recommender_system/README.md)
 1. [图像自动生成](gan/README.md)

travis/precommit.sh

+#!/bin/bash
+function abort(){
+    echo "Your commit 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
+  git diff  --exit-code
+fi
+
+trap : 0