Update to Rust nightly
Handle exit status more consistently. #211

This changes the `uumain` functions to return the exit code as `int`.

It does not eliminate all calls to `os::set_exit_status` and `libc::exit`.
Get test suite passing again by tweaking error handling in mkdir

Replace `show_error!` with Result<(), int> and `display_error!`
Make show_error! not set the exit code. #211
Make busytest stop complaining about missing config file
Fix typo
Restore error recovery behavior in rm, rmdir, etc.

These tools continue on error. This patch uses `Result` and the
`and` method to collect `Err` values.
Restore error handling to md5sum
Remove tail return statements.

Per review feedback.
phase(syntax) -> phase(plugin)
Merge pull request #212 from brson/exitcodes

Change the signature of `uumain` to return `int`
Rudamentary tail implementation.

For specific info on missing features and optimizations,
look at tail/README.md
Add the ability to install coreutils (resolves #216)
Add some installation instructions
Clarify uninstallation instructions
Merge pull request #228 from Arcterus/install-target

Add the ability to install coreutils (resolves #216)
Merge pull request #225 from molysgaard/master

Rudamentary tail implementation.
md5sum: update rust-crypto
tail: fix build by changing uint to u64
Merge pull request #230 from Arcterus/rust-crypto

Fix build