[feature] replace reader with ruby code

[masukomi]

In v1.0 we're going to be using reader on the back-end after struggling with the severe limitations of ruby-readability.

as a developer & the maintainer I want more control over the generated archive, and the removal of a significant dependency in a different language ecosystem so that I can more easily improve the archives we create and simplify installation.

This will require either finding a replacement for ruby-readability or creating a new ruby port of a modern version of the arc90 readability algorithm.