message: Added from_str for Consistency
diff: use std::convert::From;
  use std::default::Default;
  use std::io;
  +use std::str::FromStr;
  use crate::error;
  use crate::frame::{AsBytes, FromBytes, FromCursor};
  @@ -80,6 +81,34 @@ impl Default for Consistency {
  }
  }
  +impl FromStr for Consistency {
  + type Err = error::Error;
  +
  + fn from_str(s: &str) -> Result<Self, Self::Err> {
  + let consistency = match s {
  + "Any" => Consistency::Any,
  + "One" => Consistency::One,
  + "Two" => Consistency::Two,
  + "Three" => Consistency::Three,
  + "Quorum" => Consistency::Quorum,
  + "All" => Consistency::All,
  + "LocalQuorum" => Consistency::LocalQuorum,
  + "EachQuorum" => Consistency::EachQuorum,
  + "Serial" => Consistency::Serial,
  + "LocalSerial" => Consistency::LocalSerial,
  + "LocalOne" => Consistency::LocalOne,
  + _ => {
  + return Err(error::Error::General(format!(
  + "Invalid consistency provided: {}",
  + s
  + )))
  + }
  + };
  +
  + Ok(consistency)
  + }
  +}
  +
  impl AsBytes for Consistency {
  fn as_bytes(&self) -> Vec<u8> {
  match *self {
  