Remove calls to deprecated drain* methods from docs (#102)

src/bytes.rs

@@ -1111,7 +1111,7 @@ impl BytesMut {
     /// buf.put(&[0; 64][..]);
     ///
     /// let ptr = buf.as_ptr();
-    /// let other = buf.drain();
+    /// let other = buf.take();
     ///
     /// assert!(buf.is_empty());
     /// assert_eq!(buf.capacity(), 64);

src/lib.rs

@@ -29,12 +29,12 @@
 //! buf.put(&b"hello world"[..]);
 //! buf.put_u16::<BigEndian>(1234);
 //!
-//! let a = buf.drain();
+//! let a = buf.take();
 //! assert_eq!(a, b"hello world\x04\xD2"[..]);
 //!
 //! buf.put(&b"goodbye world"[..]);
 //!
-//! let b = buf.drain();
+//! let b = buf.take();
 //! assert_eq!(b, b"goodbye world"[..]);
 //!
 //! assert_eq!(buf.capacity(), 998);