Fix segmentio/metalsmith-permalinks#48, a patch to normalize() linksets.

[arccoza]

normalize() doesn't process linksets; it ensures that options.linksets exists, but doesn't apply date formatting or a default value for the relative option, as it does for basic options. This is a simple patch to ensure linksets get the same treatment.

[woodyrew]

Thanks for the PR.

Could you resolve the conflicts or create a new PR based off master? Also added tests would be great.

[arccoza]

Wow, now this is a bit of a fossil; are you trying to breathe some life back into the plugin? I haven't used metalsmith in a while, but I'll try put together a new patch for you.

[woodyrew]

The Metalsmith community have taken over the core plugins as they weren't being maintained by segment.

[webketje]

I believe this has been resolved in 2.5.x