package.json optimizations

`bin` and `lib` paths are already relative to the package.json file.

`bin` only needs to be an object if the executable name differs from `name` or when supplying multiple names.

`files` makes `npm install --production` installs much lighter.

`scripts` don't need to target executables directly as they are added to `PATH` during `npm install`.
does it work if mocha isn't installed globally?