message: Re-expose SDL keyboard modifier constants
  Resolves issue
diff: @@ -40,6 +40,10 @@ use timer;
  use std::time::Duration;
  +pub use sdl2::keyboard::{CAPSMOD, LALTMOD, LCTRLMOD, LGUIMOD, LSHIFTMOD, MODEMOD, NOMOD, NUMMOD,
  + RALTMOD, RCTRLMOD, RESERVEDMOD, RGUIMOD, RSHIFTMOD};
  +
  +
  /// A trait defining event callbacks; your primary interface with
  