Multiple fixes (added dependency on facebook/xhprof, added ability to send custom header in response & enable xhprof for requests with particular query argument)

[maxromanovsky]

1. added dependency on facebook/xhprof
2. added ability to send custom header in response
3. enable xhprof for requests with particular query argument

[stephpy]

:+1: Good improvements :)

[maxromanovsky]

Updated PR with changes to Response header. Now it contains xhprof Run ID instead of full URL to xhprof due to security reasons

[stephpy]

Thank you ;)