Supplement readme (#135)

* Switch to back to alpine v3.6
Signed-off-by: Christian Häussler <c-n-i@web.de> (github: @cniweb)

Signed-off-by: Christian Häussler <c-n-i@web.de>

* Switch back to alpine v3.6
Signed-off-by: Christian Häussler <c-n-i@web.de> (github: @cniweb)

Signed-off-by: Christian Häussler <c-n-i@web.de>

* Merge pull request #1 from openhab/master

Update from master

* Merge remote-tracking branch 'refs/remotes/openhab/master'

* Add warning for Alpine image users
Fix #130

Signed-off-by: Christian Häussler <c-n-i@web.de>