Add commonjs option

[willdady]

In addition to the amd option it would be great if there was a commonjs option, grunt-contrib-handlebars has this option and has an almost identical API to this.

This will allow the output to be 'required' in a Browserify/Node setup. Alternatively the ability to set the output file's header/footer would be good too.

[SimonChong]

+1

[dbrugne]

+1

[fkereki]

+1 - if you want to use this with TypeScript & Node, CommonJS is required.