Demo: Allow pushing/pulling/checking out individual commits

[soapy1]

ref: #42

Currently, araki only supports tagging changes to an environment. This PR demos how araki might work if it is able to use git commits in addition to tags. It adds the following features:

• Add 'araki commit' command. This command allows users to commit a change to the repo without tagging.
• List commits and tags
  • araki list will list all the commits in the project
  • araki list --tags will list all the tags in the project
• checkout tags or commits
• pushes all tags + commits by default. Also able to push all commits + a selected tag.

[soapy1]

This PR is a suggestion about how this might work. Let's play around with this and decide if this is the direction we want to go.