Auto merge of #4476 - behnam:book, r=alexcrichton

[doc/book] Move section content to */index.md

This gives a better over-all structure to the book, which we can also
follow for other books on <doc.rust-lang.org>.

Also, confirming fix for broken links with the latest (0.0.24) `mdbook`
release.

Author: bors

src/doc/MIGRATION_MAP

@@ -1,5 +1,5 @@
-index.md book/src/SUMMARY.md book/src/getting-started.md book/src/getting-started/*.md
-guide.md book/src/guide.md book/src/guide/*.md
+index.md book/src/index.md book/src/getting-started/index.md book/src/getting-started/*.md
+guide.md book/src/guide/index.md book/src/guide/*.md
 build-script.md book/src/reference/build-scripts.md
 config.md book/src/reference/config.md
 crates-io.md book/src/reference/publishing.md

src/doc/book/src/SUMMARY.md

@@ -2,11 +2,11 @@
 
 [Introduction](index.md)
 
-* [Getting Started](getting-started.md)
+* [Getting Started](getting-started/index.md)
     * [Installation](getting-started/installation.md)
     * [First Steps with Cargo](getting-started/first-steps.md)
 
-* [Cargo Guide](guide.md)
+* [Cargo Guide](guide/index.md)
     * [Why Cargo Exists](guide/why-cargo-exists.md)
     * [Creating a New Project](guide/creating-a-new-project.md)
     * [Working on an Existing Project](guide/working-on-an-existing-project.md)
@@ -16,7 +16,7 @@
     * [Tests](guide/tests.md)
     * [Continuous Integration](guide/continuous-integration.md)
 
-* [Cargo Reference](reference.md)
+* [Cargo Reference](reference/index.md)
     * [Specifying Dependencies](reference/specifying-dependencies.md)
     * [The Manifest Format](reference/manifest.md)
     * [Configuration](reference/config.md)

src/doc/book/src/getting-started/first-steps.md

@@ -67,4 +67,4 @@ Hello, world!
 
 ### Going further
 
-For more details on using Cargo, check out the [Cargo Guide](guide.html)
+For more details on using Cargo, check out the [Cargo Guide](guide/index.html)

src/doc/book/src/getting-started.md renamed to src/doc/book/src/getting-started/index.md

@@ -13,12 +13,12 @@ dependencies, compiles your project, makes packages, and upload them to
 
 To get started with Cargo, install Cargo (and Rust) and set up your first crate.
 
-**[Cargo Guide](guide.html)**
+**[Cargo Guide](guide/index.html)**
 
 The guide will give you all you need to know about how to use Cargo to develop
 Rust projects.
 
-**[Cargo Reference](reference.html)**
+**[Cargo Reference](reference/index.html)**
 
 The reference covers the details of various areas of Cargo.
 

src/doc/book/src/guide.md renamed to src/doc/book/src/guide/index.md

@@ -11,7 +11,7 @@ development. Let's take a look at how to do each of these.
 
 Cargo is configured to look for dependencies on [crates.io] by default. Only
 the name and a version string are required in this case. In [the cargo
-guide](guide.html), we specified a dependency on the `time` crate:
+guide](guide/index.html), we specified a dependency on the `time` crate:
 
 ```toml
 [dependencies]
@@ -126,12 +126,11 @@ rand = { git = "https://github.com/rust-lang-nursery/rand", branch = "next" }
 
 ### Specifying path dependencies
 
-Over time, our `hello_world` project from [the guide](guide.html) has grown
-significantly in size! It’s gotten to the point that we probably want to
-split out a separate crate for others to use. To do this Cargo supports
-**path dependencies** which are typically sub-crates that live within one
-repository. Let’s start off by making a new crate inside of our `hello_world`
-project:
+Over time, our `hello_world` project from [the guide](guide/index.html) has
+grown significantly in size! It’s gotten to the point that we probably want to
+split out a separate crate for others to use. To do this Cargo supports **path
+dependencies** which are typically sub-crates that live within one repository.
+Let’s start off by making a new crate inside of our `hello_world` project:
 
 ```shell
 # inside of hello_world/