Publish responsive-html-email-signature utility to npm

[reederz]

I see that at the moment a lot of people are forking this repo just to add their branding data. How about reworking this util into an npm module which people can install and run as script (branding data would be just an argument for the script)?. It'd work roughly like this:

# Install executable
npm install -g responsive-html-email-signature

# generate templates
responsive-html-email-signature --config-dir ./foobar --output-dir ./baz

[danmindru]

Actually we could do a new repo / package called responsive-email-cli that does that. This one can be a more beginner-friendly (and slightly limited) version of that.

Will see what makes sense when I get to it :)

[reederz]

I like that idea.