Created an app setting for whether to highlight the current line (no UI yet).
Made whether to show line numbers configurable (no UI yet).
Corrected spelling.
Fixed indentation.
Added AddTo() IEnumerable extension method.
Refactored tests to remove some of the mocking noise by using alternative syntax.
More test formatting tweaks.
Added an extension method for dictionary that returns an Option if a key doesn't exist.
Renamed Option.Do -> Apply.