Extensions aren't ever displayed in lowercase, just compared case-insensitively, so this makes sense.

The widths come pre-computed, so there's no reason to keep them around in this table anymore.

Instead of stripping the ANSI formatting characters from our strings, work out the length without them and use that. This is per-column, but most of them are simple (just the same number of characters in the non-coloured string).

Sometimes, this is really simple: for example, trwxrwxrwx permissions strings are always going to be ten characters long, and the strings that get returned are chock full of ANSI escape codes.

This should have a small benefit on performance.

- uint -> usize
- getopts Cargo library
- replace feature gates with unstable APIs

Also, remove dependency on the Regex library by replacing the one place it was used with standard code that should hopefully be faster anyway.

std::str changes, and the way macros are expanded.

Now the grids are optimised so each column is only as wide as its longest file name. The method could do with some optimising, but at least it works.