You can now have different columns per directory. So now, the Git column only appears when there's a Git repository in the current directory.

This is something that I've long wanted to add. It uses libgit2 as an optional dependency.

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

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

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

I'm serious, the more functionality I can use external crates for, the better.

Also, re-use the stat result from directory-checking.

This finally fixes the issue where trying to list a file causes a crash. Also, tidy up some of the uses of references.

Also, rename old 'lines' view to 'details' which makes more sense

- Lifetime changes in unix.rs
- lexical_ordering -> cmp
- from_utf8_lossy got moved into String
- vec.get(n) -> vec[n]

This makes it more like ls. The --long (-l) argument has been added to get at the old behaviour, and the --links argument is now on -H. I can't crib this behaviour from ls because it shows it by default.

TODO: The terminal size is currently assumed to be 80, and it uses the string length, rather than the width.