JumpToParent

Hi,

This is about adding JumpToParent feature. I was thinking that it would be really nice to see the context of the boxing function or class. This can be really useful when someone is browsing an alien codebase with large classes and functions. The jump is added to the jumplist, so it is easy to jump back. 

Sorry about the tab indentation problems I have created with my previous pull request. Now I've made a :retab before creating the pull request.

Best Regards,
Gabor