Do not ignore stdin

[Bertrand Marron]

Hey,

When using grunt-concurrent with something like grunt-nodemon it would be very interesting to have grunt-concurrent watch the standard input so I could type rs to restart the running process with nodemon.

I feel like this used to work with grunt-concurrent and now it does not anymore. Is there a reason?

Could we just replace the stdin 'ignore' with process.stdin in the spawn call?

[Sindre Sorhus]

Only a search away: https://github.com/sindresorhus/grunt-concurrent/issues?utf8=%E2%9C%93&q=stdin