Dependent package unidecode.v1 doesn't exist anymore

[victorquinn]

The stringutil imports "gopkgs.com/unidecode.v1"

https://github.com/rainycape/gondola/blob/master/util/stringutil/slug.go#L7

but that no longer exists and gives a 404 when trying to go get.

That in turn makes the stringutil package uninstallable.