Feature: Add builder run <task> -- CLI ARGS

[ryan-roemer]

Just like npm does it: https://docs.npmjs.com/cli/run-script

$ npm run-script <command> [-- <args>...]

As of npm@2.0.0, you can use custom arguments when executing scripts. The special option -- is used by getopt to delimit the end of the options. npm will pass all the arguments after the -- directly to your script:

$ npm run test -- --grep="pattern"

[ryan-roemer]

Released in builder@2.4.0