ref(contrib/coreos): remove fleet.socket from user-data

fleet.socket prevented fleet from connecting to peers on coreos 494.0.0 running on vmware.
Change prerequisites to 4GB droplets.
feat(client): add pull shortcut to global help
Merge pull request #2546 from rochacon/client/add-pull-to-global-help

Client: add pull shortcut to global help
Merge pull request #2544 from glogiotatidis/patch-1

Change prerequisites to 4GB droplets.
Merge pull request #2537 from sirwolfgang/master

ref(contrib/coreos): remove fleet.socket from user-data
docs(*): clarify local cluster settings
Merge pull request #2527 from carmstrong/clarify_installing_deis

docs(installing_deis): clarify local settings for Installing Platform