path: `resolve()` doesn't normalize drive letter on Windows

Calling `resolve()` on Windows (in Node v0.11.0+) result in a path where drive
letter case isn't always lowercase (e.g. for a relative path like '.') while
`normalize()` always returns a path with a lower case drive letter.
This eventually breaks comparisons between results of `resolve()` and
`join()` (which relies on `normalize()`) for the same path.

Fixes joyent/node#7031