Merge pull request #4 from atupal/master

advanced_foreword.rst 和 api.rst 的校对
Update sidebarintro.html
Merge pull request #5 from atupal/master

Proofreading and update of appcontext.rst
add travis-ci config #5
Merge branch 'master' of https://github.com/yinian1992/flask-docs-cn
修复一些格式错误