Suppress bundler warnings [fixes #229]

Within the gems being bundled are git repos. Bundler complains that:

    fatal: Not a git repository (or any of the parent directories): .git
    fatal: Not a git repository (or any of the parent directories): .git
    Deployment set to '/home/ubuntu/.microbosh/deployments/firstbosh/micro_bosh.yml'
    bundle exec bosh -n micro deploy /home/ubuntu/.microbosh/deployments/firstbosh/latest-micro-bosh-stemcell-aws.tgz
    fatal: Not a git repository (or any of the parent directories): .git
    fatal: Not a git repository (or any of the parent directories): .git

The ~/.microbosh ($SETTINGS) is now a git repo so as only to suppress
the bundler warning above.