Add $DOCKER_ARGS and docker-args pluginhook to dokku deploy and command run.
Add a backup-check used to validate the archive.

This allows plugins to refuse a backup, before the import process starts.
Users can force the import using -f.
Merge ssh keys rather than overwriting them.
Add a backup-check to avoid reimporting apps.
Pipe no op into docker-args plugin-hooks to avoid problems when running over ssh w/o a pty.
Merge pull request #358 from dyson/DOCKER_ARGS

For #304: Add $DOCKER_ARGS and docker-args pluginhook to dokku deploy and command run.
Merge pull request #361 from plietar/backup-check

Backup check
Reenable go test
Merge pull request #363 from progrium/2013-12-03/reenable-go

Reenable go test
Add a static website test.
Merge pull request #355 from plietar/static-test

Add a static website test.