Create image tags at build time

[tuxity]

Instead of doing a docker tag at the end of the build, we can do it directly in the docker build command (since version 1.10)

[tboerger]

Since 1.10 you can append multiple -t flags?

[tuxity]

Yes, directly into docker build command.

https://docs.docker.com/engine/reference/commandline/build/#tag-an-image--t

[Beanow]

Note, there's still a docker rmi {build.Name} command being executed at https://github.com/drone-plugins/drone-docker/pull/174/files#diff-d3a679229fa5a654b0e1d154531ac1e1R127

This change no longer builds an image with this reference name anymore though so it may not have the intended effect.

[bradrydzewski]

before merging this, we should tag a new release so that we have something to rollback to if we encounter any unforseen issues.