Remove superseded SelectionMover class

The SelectionMover class has been superseded by more flexible combinations of filters, scanners and utils. The replacements bring less dependence on the cursor node for positioning, allowing greater flexibility and re-use.

Removing this code and associated tests performs the final step necessary to close #224. In addition, this eliminates redundant line detection logic, so #225 is also closed by this as well.
I think I found a way to keep the best of both worlds. I've added an ``init`` method that takes care of turning the array into an object.

I did some quick performance checks and generally the array indexOf method is significantly slower as it has to search the full array for the majority of the nodes (https://gist.github.com/peitschie/939e447cc2984f9ea9f1).