Add Debbie's build badge (prefix badges with the name of the bot)

git-svn-id: http://svn.osgeo.org/postgis/trunk@14310 b70326c6-7e19-0410-871a-916f4a2858ee

Author: robe2

README.md

@@ -1,5 +1,5 @@
-[![Build Status](https://secure.travis-ci.org/postgis/postgis.png)]
-(http://travis-ci.org/postgis/postgis)
+Travis: [![Build Status](https://secure.travis-ci.org/postgis/postgis.png)]
+(http://travis-ci.org/postgis/postgis) Debbie: [![Build Status](http://debbie.postgis.net:8080/buildStatus/icon?job=PostGIS_2.3)](http://debbie.postgis.net:8080/view/PostGIS/job/PostGIS_2.3/)
 
 This file is here to play nicely with modern code repository facilities.
 Actual readme is [here](README.postgis).