message: fix CassandraType::BigInt
diff: @@ -7,7 +7,7 @@ use super::prelude::{Blob, Decimal};
  #[derive(Debug, PartialEq, Clone)]
  pub enum CassandraType {
  Ascii(String),
  - Bigint(BigInt),
  + Bigint(i64),
  Blob(Blob),
  Boolean(bool),
  Counter(i64),
  @@ -77,7 +77,7 @@ pub mod wrappers {
  }
  pub fn bigint(bytes: &CBytes, col_type: &ColTypeOption) -> CassandraType {
  - let t = as_rust_type!(col_type, bytes, BigInt).unwrap();
  + let t = as_rust_type!(col_type, bytes, i64).unwrap();
  match t {
  Some(t) => CassandraType::Bigint(t),
  