message: Fix misleading comments on write_be and read_be.
diff: @@ -385,8 +385,7 @@ pub trait PrimeFieldRepr: Sized +
  /// Performs a leftwise bitshift of this number by some amount.
  fn shl(&mut self, amt: u32);
  - /// Writes this `PrimeFieldRepr` as a big endian integer. Always writes
  - /// `(num_bits` / 8) bytes.
  + /// Writes this `PrimeFieldRepr` as a big endian integer.
  fn write_be<W: Write>(&self, mut writer: W) -> io::Result<()> {
  use byteorder::{WriteBytesExt, BigEndian};
  @@ -397,8 +396,7 @@ pub trait PrimeFieldRepr: Sized +
  Ok(())
  }
  - /// Reads a big endian integer occupying (`num_bits` / 8) bytes into this
  - /// representation.
  + /// Reads a big endian integer into this representation.
  fn read_be<R: Read>(&mut self, mut reader: R) -> io::Result<()> {
  use byteorder::{ReadBytesExt, BigEndian};
  