Allow parsing remaining segments

[michalmuskala]

This adds a parser for returning the remaining segments as a list of strings.

It's extremely useful in dynamic routing situations, where the routing reflects a file system hierarchy - I found no way to achieve such behaviour with the already present functions.

[process-bot]

Thanks for the pull request! Make sure it satisfies this checklist. My human colleagues will appreciate it!

Here is what to expect next, and if anyone wants to comment, keep these things in mind.

[nickmiller-wf]

My project really needs this.

[evancz]

This is pretty straight forward to add, so I can add it myself if that makes sense after I review this library.

[nickmiller-wf]

thanks @evancz!