Reduce auto-installed dependencies if provisioning a released version of Deis

[sgoings]

@rimusz encountered the experience that rigger installs the following packages when provisioning a release version of deis:

• git
• go
• docker-machine

Let's move the auto installation of these tools later in the process of the run lifecycle of rigger or remove the dependencies entirely (gasp!).

[rimusz]

@sgoings for the release version the dependencies should be entirely removed :)

[bacongobbler]

Is this baked into rigger or is this when installing it from a package installer like homebrew? If it's the latter I think it's completely reasonable to let the dependency mgmt program handle it unless it's causing dependency hell on newcomers :)