The more I think about it, the more I'd like to support:

$ ncc run

and

$ ncc build

We would:

• Add support for pkg.main / index.js if no argument is supplied
• run to build to a temporary location and clean it up on a best-effort basis
• build to output to a default dist directory if -o is not supplied (in tandem with Ditch stdout and make -o be a directory #30)