Update all-contributors badge to new version

Author: tkoyama010

README.md

@@ -1,7 +1,5 @@
 # <img src="https://www.pyopensci.org/images/logo.png" width=100 /> pyOpenSci scientific Python Packaging Guide
-<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
-[![All Contributors](https://img.shields.io/badge/all_contributors-75-orange.svg?style=flat-square)](#contributors-)
-<!-- ALL-CONTRIBUTORS-BADGE:END -->
+[![All Contributors](https://img.shields.io/github/all-contributors/pyOpenSci/python-package-guide?color=ee8449)](#contributors)
 
 ![GitHub release (latest by date)](https://img.shields.io/github/v/release/pyopensci/python-package-guide?color=purple&display_name=tag&style=plastic)