latest docker tag is different than 0.1.3

Hi! 

I have a project to pilot the use of this tool over gettext  and noticed that the :`latest` tag published to dockerhub is 6mo newer and slightly larger than the  latest release (`0.1.3`) tag. 

https://hub.docker.com/r/stephenc/envsub/tags

did something change in the build? are we safe to use 0.1.3 tag?

Thanks so much for this tool!

~ Brice