Add --all option

[mtylty]

Add a --all option that makes it easy to deploy (or run a command) on every configured app.

Something like:

pulsar cap -c nebulab/conf --all deploy

We should also consider if this is useful/feasible:

pulsar cap -c nebulab/conf --all --only-sinatra deploy

pulsar cap -c nebulab/conf --all --only-rails deploy

pulsar cap -c nebulab/conf --all --only-rails-3 deploy

pulsar cap -c nebulab/conf --all --only-rails-3-1 deploy

[kennyadsl]

We can even think about some per app batch deploy feature like:

cap -c nebulab/conf project1 --all-stages deploy

which will deploy to all project1 stages. 👍

[mtylty]

This issue is too complicated as is.

To make it simple I added a way (c879945) to deploy multiple apps (on the same stage) by using a comma separated list of apps.

It makes no sense to me to deploy multiple stages so I've left out that feature.