min_len and max_len don't work for strings

[not-my-profile]

#[derive(Validate)]
struct Thing {
    #[validatron(min_len = 5)]
    pub name: String
}

fails with:

&std::string::String is not an iterator
the trait Iterator is not implemented for &std::string::String
required because of the requirements on the impl of IntoIterator for &std::string::String

[spire-ffoston]

Thanks for raising this, I made a concious decision to not support string lengths initially to prevent any confusion with str::len() vs str::char() potentially returning different sizes.

It's on the todo list so I'll get around to adding a propper string length validator eventually.