Release v3.1.0

Feature/class (#8)

* Convert listeners to class

First step in converting everything to classes.
A lot of `this`.

* Convert paths to class

* Convert pathifier to class

* Convert Data (index) to class

* Convert index to data

index doesn't have data any more, but it's moved
to data.ts.

* 3.0.0

* Bump dependencies

+ npm audit fix

* 3.1.0

* Convert a forEach loop to for of

Fixes linting warning about variable in loop in function thingy.