Breaking: ignore node_modules by default (fixes #1163)

Doesn't look like it:

```js
// Argument order is (path, pattern)
minimatch("node_modules/file.js", "node_modules/**") // => true
minimatch("subdir/node_modules/file.js", "node_modules/**") // => false
minimatch("subdir/node_modules/file.js", "./node_modules/**") // => false
// ...and here's an interesting case
minimatch("node_modules/file.js", "./node_modules/**") // => false
```

I've added a test case and amended the commit just to be sure.