FixedString seems broken

[dzbarsky]

This line doesn't seem correct to me:

clickhouse-rs/src/types/column/fixed_string.rs

Line 70 in b7f0df4

self.buffer.resize(old_len + (self.str_len - l), 0_u8);

Let's take a closer look at the implementation:

    fn push(&mut self, value: Value) {
        let bs: String = String::from(value);
        let l = cmp::min(bs.len(), self.str_len);
        let old_len = self.buffer.len();
        self.buffer.extend_from_slice(&bs.as_bytes()[0..l]);
        self.buffer.resize(old_len + (self.str_len - l), 0_u8);
    }

In the case when the string in value is of the correct size, l = self.str_len() and we extend self.buffer with the new string, then we proceed to call self.buffer.resize(old_len, 0u8) which truncates the buffer to what it was before we did the write. We should probably resize starting at the new length, not the old one?