This commit uses Clippy to fix all the 'use_self' warnings. Using Self instead of the type name has been good Rust style for a while now, and it's become the style I'm used to seeing.
The goal of this part of the refactoring, if you wondered, is to make it so only the tree module is aware that it needs ‘depth’ and ‘last’ values to draw the tree.
As far as the details module is concerned, it should just be doing something to produce TreeParams values which it later consumes; that’s it.
This change should make it easier to have tables that may or may not have a tree in them.
This commit removes the 'main' function present in main.rs, renames it to exa.rs, and puts the 'main' function in its own binary. This, I think, makes it more clear how the program works and where the main entry point is.
Librarification also means that we can start testing as a whole. Two tests have been added that test everything, passing in raw command-line arguments then comparing against the binary coloured text that gets produced.
Casualties include having to specifically mark some code blocks in documentation as 'tests', as rustdoc kept on trying to execute my ANSI art.
This commit separates the code used to generate the tree structure characters from the code used to build tables, meaning that it'll become possible to display tree structures without using any of the table code.
Also, some tests are added to make sure that the tree code *basically* works.
