Add additional dependencies to install instructions

[tribou]

I ran into an issue where my deployed revisions were not being listed. Fortunately, I happened across the ember-cli-deploy-display-revisions repo which fixed the issue; and I thought it would help others if all the dependencies needed for the basic deployment commands used by ember-cli-deploy-redis were listed in the README.

[achambers]

Hi @tribou. Thanks so much for this. We've had some discussion around this and agree that it's useful info for new users. However, I think it's more appropriate in a section of it's own along the same lines as Activation.

The revisions (and activation) aren't required for using this plugin and therefore they don't really belong in the Quickstart section. That section is more for "these are the basic things you need to do to get up and running with this plugin". Instead, it feels like the revision info is better placed in it's own section.

Are you happy to make the relevant changes?

Thanks again for your input and suggesting this. Will merge the PR when it's ready.

[ghedamat]

@tribou friendly ping :)

thanks again for this in the meantime!

[tribou]

Sorry for the delay on this!

[ghedamat]

thanks @tribou