Fix Elm version in Dockerfile (#901)
Fix Elm version in Dockerfile (#901)

Signed-off-by: Dušan Borovčanin <678243bfa09a6ebf4a586bfa2057e53cece31497@mainflux.com>
drasko/mainflux,Mainflux/mainflux-lite,drasko/mainflux,drasko/mainflux