"The Rust Programming Language"

This pulls all of our long-form documentation into a single document,
nicknamed "the book" and formally titled "The Rust Programming
Language."

A few things motivated this change:

* People knew of The Guide, but not the individual Guides. This merges
  them together, helping discoverability.
* You can get all of Rust's longform documentation in one place, which
  is nice.
* We now have rustbook in-tree, which can generate this kind of
  documentation. While its style is basic, the general idea is much
  better: a table of contents on the left-hand side.
* Rather than a almost 10,000-line guide.md, there are now smaller files
  per section.

RELEASES.md

@@ -19,8 +19,10 @@ Version 1.0.0-alpha (January 2015)
       distribution into the Cargo ecosystem so they can evolve
       separately and don't need to be stabilized as quickly, including
       'time', 'getopts', 'num', 'regex', and 'term'.
-    * Documentation continues to be expanded with more guides, more
-      API coverage and more examples.
+    * Documentation continues to be expanded with more API coverage, more
+      examples, and more in-depth explanations. The guides have been
+      consolidated into [The Rust Programming Language][trpl].
+    * "Rust By Example" is now maintained by the Rust team.
     * All official Rust binary installers now come with [Cargo], the
       Rust package manager.
 
@@ -179,6 +181,7 @@ Version 1.0.0-alpha (January 2015)
 [objsafe]: https://github.com/rust-lang/rfcs/blob/master/text/0255-object-safety.md
 [assoc]: https://github.com/rust-lang/rfcs/blob/master/text/0195-associated-items.md
 [ints]: https://github.com/rust-lang/rfcs/pull/544#issuecomment-68760871
+[trpl]: http://doc.rust-lang.org/book/index.html
 
 Version 0.12.0 (October 2014)
 -----------------------------