feat: support package.json config

[zekth]

fix #235

So this line is a bit ugly:

return require(path.join(process.cwd(), 'package.json')).madge;

But due to eslint i'm forced to do it because of the nosync rule. Making the fs lookup for the package.json async would wrap everything up into a promise; which involves more coding for not so much benefit.

Let me know your thoughts about it.

[pahen]

Published in v3.7.0