Enable warnings in stdout

[janetkuo]

Ref #71

With this change, you see warnings even when --stdout is specified:

$ kompose convert -f docker-voting.yml -y --stdout | kubectl create -f - 
time="2016-08-03T11:39:37-07:00" level=warning msg="Unsupported key build - ignoring" 
time="2016-08-03T11:39:37-07:00" level=warning msg="Unsupported key networks - ignoring" 
time="2016-08-03T11:39:37-07:00" level=warning msg="[worker] Service cannot be created because of missing port." 
time="2016-08-03T11:39:37-07:00" level=warning msg="[db] Service cannot be created because of missing port." 
service "redis" created
service "result" created
service "vote" created
deployment "db" created
deployment "redis" created
Error from server: error when creating "STDIN": Deployment.extensions "vote" is invalid: spec.template.spec.containers[0].image: Required value
Error from server: error when creating "STDIN": Deployment.extensions "worker" is invalid: spec.template.spec.containers[0].image: Required value
Error from server: error when creating "STDIN": Deployment.extensions "result" is invalid: spec.template.spec.containers[0].image: Required value

[janetkuo]

However we need to solve this in a separate PR/issue; filed #80

Error from server: error when creating "STDIN": Deployment.extensions "vote" is invalid: spec.template.spec.containers[0].image: Required value
Error from server: error when creating "STDIN": Deployment.extensions "worker" is invalid: spec.template.spec.containers[0].image: Required value
Error from server: error when creating "STDIN": Deployment.extensions "result" is invalid: spec.template.spec.containers[0].image: Required value

[ngtuna]

Ah... so it means we can still print warning message and the pipeline ignores it... So actually my previous commit 72fc1a2 is unnecessary...

[janetkuo]

Yes, I believe those warnings are printed to stderr so it won't mingle with real output