Support for CLI args

[johnny-bit]

Hi,

Tools like ttf2woff and ttf2eot support following CLI syntax:

ttf2THING input.ttf output.THING

It would greatly simplify handling of multiple extensions 👍

[nfroidure]

Would accept a PR using commander and working like svgicons2svgfont. Extra options like useing the JS version or the compiled one would be great too.