latest tag missing on DockerHub

[MatthewTingum]

I'm running back through some old issues and I came across this.

The readme states that you should do the following to grab the latest docker image:

$ docker pull jsychong/metaboanalyst

Doing that results in an error:

Using default tag: latest
Error response from daemon: manifest for jsychong/metaboanalyst:latest not found: manifest unknown: manifest unknown

Pulling from a specific tag works:

$ docker pull jsychong/metaboanalyst:august2020

I'd recommend pulling from tagged images and documenting the same.