readme: Add build status

README.md

@@ -7,6 +7,7 @@ Oragono is a fork of the [Ergonomadic](https://github.com/edmund-huber/ergonomad
 ---
 
 [![Go Report Card](https://goreportcard.com/badge/github.com/oragono/oragono)](https://goreportcard.com/report/github.com/oragono/oragono)
+[![Build Status](https://travis-ci.org/oragono/oragono.svg?branch=master)](https://travis-ci.org/oragono/oragono)
 [![Download Latest Release](https://img.shields.io/badge/downloads-latest%20release-green.svg)](https://github.com/oragono/oragono/releases/latest)
 [![Freenode #oragono](https://img.shields.io/badge/Freenode-%23oragono-1e72ff.svg?style=flat)](https://www.irccloud.com/invite?channel=%23oragono&hostname=irc.freenode.net&port=6697&ssl=1)