Add grid view by default

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.
Colour file names in grid view
Correctly calculate number of rows
Add --across parameter
Don't pad the final column
Upgrade to latest Rust nightly

- change to_string() on numbers to to_str()
Upgrade to latest Rust nightly

- Lifetime changes in unix.rs
- lexical_ordering -> cmp
- from_utf8_lossy got moved into String
- vec.get(n) -> vec[n]
Use string width, rather than length, to calculate column size
Get terminal width for grid view (resolve #1)
Merge pull request #3 from ogham/grid-view

Grid view