[src/doc/book] Fix header casings

Author: behnam

src/doc/book/src/01-02-first-steps.md

@@ -1,4 +1,4 @@
-## First steps with Cargo
+## First Steps with Cargo
 
 To start a new project with Cargo, use `cargo new`:
 

src/doc/book/src/02-01-why-cargo-exists.md

@@ -1,4 +1,4 @@
-## Why Cargo exists
+## Why Cargo Exists
 
 Cargo is a tool that allows Rust projects to declare their various
 dependencies and ensure that you’ll always get a repeatable build.

src/doc/book/src/02-02-creating-a-new-project.md

@@ -1,4 +1,4 @@
-## Creating a new project
+## Creating a New Project
 
 To start a new project with Cargo, use `cargo new`:
 

src/doc/book/src/02-03-working-on-an-existing-project.md

@@ -1,4 +1,4 @@
-## Working on an existing Cargo project
+## Working on an Existing Cargo Project
 
 If you download an existing project that uses Cargo, it’s really easy
 to get going.

src/doc/book/src/02-05-project-layout.md

@@ -1,4 +1,4 @@
-## Project layout
+## Project Layout
 
 Cargo uses conventions for file placement to make it easy to dive into a new
 Cargo project:

src/doc/book/src/02-08-continuous-integration.md

@@ -1,4 +1,4 @@
-## Continuous integration
+## Continuous Integration
 
 ### Travis CI
 

src/doc/book/src/SUMMARY.md

@@ -2,14 +2,14 @@
 
 * [Getting Started](getting-started.md)
     * [Installation](01-01-installation.md)
-    * [First steps with Cargo](01-02-first-steps.md)
+    * [First Steps with Cargo](01-02-first-steps.md)
 
-* [Guide](guide.md)
-    * [Why Cargo exists](02-01-why-cargo-exists.md)
-    * [Creating a new project](02-02-creating-a-new-project.md)
-    * [Working on an existing Cargo project](02-03-working-on-an-existing-project.md)
+* [Cargo Guide](guide.md)
+    * [Why Cargo Exists](02-01-why-cargo-exists.md)
+    * [Creating a New Project](02-02-creating-a-new-project.md)
+    * [Working on an Existing Project](02-03-working-on-an-existing-project.md)
     * [Dependencies](02-04-dependencies.md)
-    * [Project layout](02-05-project-layout.md)
+    * [Project Layout](02-05-project-layout.md)
     * [Cargo.toml vs Cargo.lock](02-06-cargo-toml-vs-cargo-lock.md)
     * [Tests](02-07-tests.md)
     * [Continuous Integration](02-08-continuous-integration.md)