Deserialize to sequence of enum types

[jerry73204]

The patch deals with repeated top level sections. For example,

[person]
name = "Ana"

[person]
name = "Box"

It enables the deserialization into a sequence of enum types. The code below will work out of box.

#[derive(Debug, Clone, PartialEq, Eq, Hash, Serialize, Deserialize)]
enum Person {
    pub name: String
}

let people: Vec<Person> = serde_ini::from_str(ini_text)?;

[jerry73204]

The patch has an extra commit that runs rustfmt on the whole repo.

[arcnmx]

Sorry this took so long to get to - merged as 53fe15c4de8b415661b9697f48870fea079b436b without the formatting changes. I still need to mull over how to use rustfmt...