Add command line help text for new subcommand 'cargo test'
Remove superfluous newline
Use a custom rm_rf to paper over windows git funkiness
auto merge of #81 : alexcrichton/cargo/fix-windows, r=wycats
auto merge of #75 : samebchase/cargo/add-help-for-test, r=alexcrichton
Generalise `find_project` to not always search parents.

Also, add a helper around `find_project` that returns `dir/file` rather
than just `dir`.
Check for the existence of Cargo.toml when reading packages.

Fixes #82.