Fix parsed URL caching in Request object

More care is needed when caching the parsed url in restify.Request to
prevent propagating stale data if req.url is later updated.

This issue was reproducible when using the pre.sanitizePath handler and
tracing route-start via dtrace.

Reviewed-By: Timothy J Fontaine <tjfontaine@gmail.com>
Update dependencies for node v0.11 compatibility

- dtrace-provider: Support node v0.11
- bunyan: Use updated dtrace-provider
- backoff: Fix memory leak
Release version 2.8.4