`release_path` will now return the value of `current_path` by default.
Tasks that create a new release (i.e. `deploy`) now explicitly over-ride this
default with a new release path. This change allows tasks that run in both
deploy and non-deploy contexts to use `release_path` to target the latest
release when run in isolation, and the new release (before it is `current`)
when run as part of a deploy.
This commit adds the outlines of a testing framework for Cap tasks.
Currently just the `cap install` and `cap deploy` tasks are covered. For
now, these tests can only be run if it is `ssh localhost` will work for
you and are currently excluded from the suite. It is my intention to
eventually replace the `sshkit` backend with a test backend, but for now
this is good enough to prevent simple regressions.
