Merge pull request #60 from sue445/sue445-patch-1

Add pixela badge

README.md

@@ -3,6 +3,7 @@
 [Pixela](https://pixe.la/) API client for Ruby
 
 [![Gem Version](https://badge.fury.io/rb/pixela.svg)](https://badge.fury.io/rb/pixela)
+[![CI activity of pixela-gem](https://pixe.la/v1/users/sue445/graphs/pixela-gem-ci?mode=badge)](https://pixe.la/v1/users/sue445/graphs/pixela-gem-ci.html)
 [![Build Status](https://travis-ci.org/sue445/pixela.svg?branch=master)](https://travis-ci.org/sue445/pixela)
 [![Maintainability](https://api.codeclimate.com/v1/badges/4c6316222717ee809b57/maintainability)](https://codeclimate.com/github/sue445/pixela/maintainability)
 [![Coverage Status](https://coveralls.io/repos/github/sue445/pixela/badge.svg)](https://coveralls.io/github/sue445/pixela)