Revert "url: support `path` for url.format"

This reverts commit d312b6d1.

Reverted for breaking npm install with git+ssh URLs. See also the fix-up in commit a1e54d6f.

Conflicts: doc/api/url.markdown

Fixes: https://github.com/iojs/io.js/issues/295

R=@evanlucas or @rvagg, /cc @yorkie