Allow output to stdout

[codingtony]

I have found your project after using handlebars-cmd for a while.

I needed an updated version of handlebars since handlebars-cmd depends on an old version of handlebars.

It does everything ok but it would be very nice being able to output to stdout this way I could use the tool this way :

hbs --stdout --data data.json /templates/install.hbs  > install.sh

[keithamus]

Great idea! Fancy making a PR?

[keithamus]

@codingtony https://github.com/keithamus/hbs-cli/releases/tag/v1.1.0 😄 🎉

[codingtony]

@keithamus thanks!