Support for Unmarshalling Slices of floats/ints/bools

[Gamma169]

Unless I'm mistaken, it seems that this library cannot support types of a slice of primitives other than strings.

Looking into request.go, I see functions for handling string slices and struct slices, but not slices for floats or ints or bools.

I have a struct as such:

type MyStruct struct {
  MyAttr   []string   `jsonapi:"attr,my-attr"`
}

but when I try to unmarshall it, it throws this error:
data is not a jsonapi representation of '*main.MyStruct'

Any way we could get support for this? Possibly in a more extensible fashion than just creating a new function for each.