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

This reverts commit d312b6d1.

Reverted for breaking `npm install` with git+ssh URLs.

Conflicts:
    doc/api/url.markdown

Fixes: https://github.com/iojs/io.js/issues/295
PR-URL: https://github.com/iojs/io.js/pull/303


Reviewed-By: Rod Vagg <rod@vagg.org>