Add ability to deploy npm package (tarball)

See also: https://github.com/strongloop/strong-pm/pull/12
Sorry to nitpick here... but I like error messages to be no longer than necessary...
`HTTP error occured while deploying to http://localhost:1234` would be better as something shorter, like
```
util.format(`Deploy `%s` to `%s` failed: %s`, branchOrPack, URL, err.message)
```

1. "while deploying" redundant, this is `slc deploy`, there are no other "whiles"
2. "HTTP", and if url is "https"?

err.message is readable enough.