Reworked basic trait impls

hw6/task2/src/shell.rs

 }
 
 impl BufRead for Shell<R, W> {
+    fn fill_buf(&mut self) -> Result<&[u8]> {}
+    fn consume(&mut self, amt: usize) {}
 }
 
 impl Write for Shell<R, W> {
     fn write(&mut self, buf: &[u8]) -> Result<usize> {}
     fn flush(&mut self) -> Result<()> {}
-    fn write_all(&mut self, buf: &[u8]) -> Result<()> {}
-    fn write_format(&mut self, fmt: Arguments) -> Result<()> {}
-    fn by_ref(&mut self) -> &mut Self where Self: Sized, {}
 }