message: Add Error trait for DeviceError
diff: @@ -4,6 +4,8 @@ use std::ptr;
  use std::mem;
  use vk;
  use device::Device;
  +use std::error::Error;
  +use std::fmt;
  use RawPtr;
  use version::{FunctionPointers, V1_0};
  use version::DeviceLoader;
  @@ -14,6 +16,25 @@ pub enum DeviceError {
  VkError(vk::Result),
  }
  +impl fmt::Display for DeviceError{
  + fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result{
  + write!(f, "DeviceError::{:?}", self)
  + }
  +}
  +
  +impl Error for DeviceError {
  + fn description(&self) -> &str {
  + "DeviceErrorr"
  + }
  +
  + fn cause(&self) -> Option<&Error>{
  + if let &DeviceError::VkError(ref err) = self{
  + return err.cause();
  + }
  + None
  + }
  +}
  +
  #[derive(Clone)]
  pub struct Instance<V: FunctionPointers> {
  handle: vk::Instance,
  