增加 lazy_pinyin 函数

[Huang Huang]

与 pinyin 函数的区别是： 返回值类型是 Vec<String>

let hans = "**人";
let mut args = pinyin::Args::new();

// 输出 [["zhong"] ["guo"] ["ren"]]
println!("{:?}",  pinyin::pinyin(hans, &args));

// 输出 ["zhong", "guo", "ren"]
println!("{:?}",  pinyin::lazy_pinyin(hans, &args));