Adds CLI Tool

[dsc]

Adds a simple CLI tool to decode a file/stdin and write the JSON to a file/stdout, along with updating the README. (Also moves the test files into /test).

[hughsk]

Nice work, thanks for this @dsc! There's a few stylistic differences which I'll tweak before merging, will get to it soon though :)

[dsc]

I typically write Coco (a dialect of coffee), so I'm guessing it has to do with whitespace and a burning desire for semi-colons...