Fix errors and warnings with current rust nightly

src/byte_buf.rs

 use {alloc, Bytes, SeqByteStr, MAX_CAPACITY};
 use traits::{Buf, MutBuf, MutBufExt, ByteStr};
 use std::{cmp, ptr};
-use std::num::UnsignedInt;
 
 /*
  *
@@ -57,7 +56,7 @@ impl ByteBuf {
         }
 
         // Round the capacity to the closest power of 2
-        capacity = UnsignedInt::next_power_of_two(capacity);
+        capacity = capacity.next_power_of_two();
 
         // Allocate the memory
         let mem = alloc::HEAP.allocate(capacity as usize);

src/lib.rs

 #![crate_name = "bytes"]
 #![unstable]
 
-#![feature(alloc, core, io, unsafe_no_drop_flag)]
+#![feature(alloc, core, unsafe_no_drop_flag)]
 
 pub use byte_buf::{ByteBuf, ROByteBuf, MutByteBuf};
 pub use byte_str::{SeqByteStr, SmallByteStr, SmallByteStrBuf};

src/ring.rs

 use super::{Buf, MutBuf};
 use std::{cmp, fmt, mem, ptr, slice};
-use std::num::UnsignedInt;
 use std::rt::heap;
 
 /// Buf backed by a continous chunk of memory. Maintains a read cursor and a
@@ -27,7 +26,7 @@ impl RingBuf {
         }
 
         // Round to the next power of 2 for better alignment
-        capacity = UnsignedInt::next_power_of_two(capacity);
+        capacity = capacity.next_power_of_two();
 
         // Allocate the memory
         let ptr = unsafe { heap::allocate(capacity, mem::min_align_of::<u8>()) };

test/test_seq_byte_str.rs

@@ -26,7 +26,7 @@ pub fn test_index() {
 }
 
 #[test]
-#[should_fail]
+#[should_panic]
 pub fn test_index_out_of_range() {
     let s = SeqByteStr::from_slice(gen_bytes(2000).as_slice());
     let _ = s[2001];

test/test_small_byte_str.rs

@@ -26,7 +26,7 @@ pub fn test_index() {
 }
 
 #[test]
-#[should_fail]
+#[should_panic]
 pub fn test_index_out_of_range() {
     let s = SmallByteStr::from_slice(gen_bytes(3).as_slice()).unwrap();
     let _ = s[2001];