autobuild no longer working in dockerhub

[guzzijones]

The readme says this will auto build on dockerhub on push. Let's see if that still works...

Originally posted by @cognifloyd in #124 (comment)

Where in the readme does it state that? I don't see that here.
I guess we need to build here and push to dockerhub

[cognifloyd]

https://github.com/StackStorm/st2packaging-dockerfiles/blob/master/packagingbuild/README.md