Fix Gitter.im badge
Fix Gitter.im badge

[skip ci]

purpleP/docker-postgis-1,imatia-smartgovernment/docker-postgis,LukeSwart/appropriate-postgis,elcodedocle/docker-postgis,nullcode/docker-postgis,appropriate/docker-postgis,ajaali/docker-postgis,gpavlidi/docker-postgis,moofish32/docker-postgis