grunt.config.set the version number for other tasks/uses


Set the version number into a config variable so that it can be used as `<%= pkg_version%> `in file names and passed as local variables to templates etc. This would remove the need to keep parsing the `package.json` file and is more convenient. It could remove the need to run a file re-namer as a separate task. 

My first attempt at giving back to opensource something that I have modified for my own use.

I hope it fits.