Restructure and trim down the library

This commit is a significant overhaul of the library in an effort to head
towards a stable API. The rope implementation as well as a number of buffer
implementations have been removed from the library and will live at
https://github.com/carllerche/bytes-more while they incubate.

**Bytes / BytesMut**

`Bytes` is now an atomic ref counted byte slice. As it is contigous, it offers
a richer API than before.

`BytesMut` is a mutable variant. It is safe by ensuring that it is the only
handle to a given byte slice.

**AppendBuf -> ByteBuf**

`AppendBuf` has been replaced by `ByteBuf`. The API is not identical, but is
close enough to be considered a suitable replacement.

**Removed types**

The following types have been removed in favor of living in bytes-more

* RingBuf
* BlockBuf
* `Bytes` as a rope implementation
* ReadExt
* WriteExt

src/lib.rs

@@ -1,36 +1,22 @@
-#![crate_name = "bytes"]
-#![deny(warnings)]
+//! Provides abstractions for working with bytes.
+
+#![deny(warnings, missing_docs)]
 
-#[macro_use]
-extern crate log;
 extern crate byteorder;
 
-// Implementation in here
-mod imp;
-// TODO: delete
-mod alloc;
+mod buf;
+mod bytes;
 
-pub use imp::buf::{Buf, MutBuf, IntoBuf};
-pub use imp::bytes::Bytes;
-
-pub mod buf {
-    //! Traits, helpers, and type definitions for working with buffers.
-
-    pub use imp::buf::{
-        Source,
-        Sink,
-        Reader,
-        ReadExt,
-        Writer,
-        WriteExt,
-        Fmt,
-    };
-
-    pub use imp::buf::slice::SliceBuf;
-    pub use imp::buf::append::AppendBuf;
-    pub use imp::buf::block::{BlockBuf, BlockBufCursor};
-    pub use imp::buf::bound::{BoundBuf};
-    pub use imp::buf::ring::RingBuf;
-    pub use imp::buf::take::Take;
-    pub use imp::bytes::BytesBuf;
-}
+pub use buf::{
+    Buf,
+    BufMut,
+    IntoBuf,
+    Source,
+    Sink,
+    Reader,
+    Writer,
+};
+pub use buf::byte::{ByteBuf};
+pub use buf::slice::{SliceBuf};
+pub use buf::take::{Take, TakeMut};
+pub use bytes::{Bytes, BytesMut};