sort added to search

[SunnysideAaron]

just in case anyone finds this. sorting hasn't been added to search even though it is in the api. I was about to fork and add but I found someone else already did.

https://github.com/Recordfy/go-discogs

master...Recordfy:go-discogs:master

[SunnysideAaron]

That branch doesn't have sort order. I've created a pr. #59