Use [[bin]] instead of [[executable]] in manifest examples
Add version command, closes #201
Update to master
auto merge of #219 : alexcrichton/cargo/update-to-mater, r=burningtree
auto merge of #212 : fhahn/cargo/version, r=alexcrichton

This PR adds a rustc style version command
Update hammer to fix `cargo build -h`.
auto merge of #217 : gchp/cargo/docs, r=alexcrichton

There were inconsistencies in the manifest file between using `[[bin]]` and `[[executable]]`. I've changed the examples to use `[[bin]]` for consistency.
auto merge of #220 : erickt/cargo/master, r=alexcrichton

Please don't land this until https://github.com/wycats/hammer.rs/pull/12 is landed, or else it will break the build.
Blow away all directories/files on each build

And aftewards selectively move them back into place if they're fresh. This
prevents stale files from showing up from old builds.

This currently breaks anyone build `build=` scripts, the fix is coming in the
next commit.

Closes #205
House all native build output in a per-package dir

In order to ensure there are no stale artifacts as part of a build, this commit
houses all output of native build commands in their own directories. Each
directory is on a per-package basis, and the output is preserved if the package
is fresh or discarded if it is not.

This does not remove the DEPS_DIR environment variable, it just wires it to the
same value as OUT_DIR.