serde support?

[minghuaw]

What's the best way to introduce serde support for Array? We would need to serialize/deserialize both shape and data at the minimum. What about introducing a new type that implement Serialzie and Deserialize? eg.

#[derive(Serialize, Deserialize)]
struct ArrayDescriptor<'a, T> {
    shape: &'a [i32],
    data: &'a [T]
}