Command line support

[mmaelzer]

Interested in a PR to add command line support? mmaelzer@678411b

Allows index.js to be called like

node index.js #fff
// rgb(255,255,255)

or if you chmod +x the index.js file...

./index.js #fff
// rgb(255,255,255)

[kamicane]

I think bin/rgb would be better suited for the purpose than embedding it in the main.

[mmaelzer]

That's reasonable. Would you accept mmaelzer@b996165?

[kamicane]

Looks good, can you -x index.js and send a pull req?

Ty!