Update go-querystring to a version that handles references to slices properly

[Bouwdie]

@svanharmelen Thanks for the commits and the fix. I unfortunately am not used to the new review interface of github and didn't push my remarks. One this I would like to stress is to update the go-querystring dependency, refences to slices will otherwise not be encoded properly aka project.Tags[] for example. Thanks again 💯

Originally posted by @Bouwdie in #1318 (comment)