Test and build the book on travis

.travis.yml

@@ -3,24 +3,28 @@ language: rust
 env:
   - RUSTFLAGS="-D warnings"
 
-before_script:
-  - rustup component add rustfmt
-
 matrix:
   fast_finish: true
   include:
     - rust: nightly
       os: linux
-      env: BUILD_DOCS=1
+      env: BUILD_DOCS=1 BUILD_BOOK=1
     - rust: nightly
       os: osx
       osx_image: xcode9.2
       env: BUILD_DOCS=1
     - rust: nightly-x86_64-pc-windows-msvc
       os: windows
 
+before_script:
+  - rustup component add rustfmt
+  - (test -x $HOME/.cargo/bin/cargo-install-update || cargo install cargo-update)
+  - (test -x $HOME/.cargo/bin/mdbook || cargo install --vers "^0.3" mdbook)
+  - cargo install-update -a
+
 script:
-  - cargo check --all --benches --bins --examples --tests
-  - cargo test --all
+  - if ![[ -n "$BUILD_BOOK" ]]; then cargo check --all --benches --bins --examples --tests && cargo test --all; fi
+  - if  [[ -n "$BUILD_BOOK" ]]; then cargo test  --all --benches --bins --examples --tests; fi
   - cargo fmt --all -- --check
-  - if [[ -n "$BUILD_DOCS" ]]; then cargo doc --features docs; fi
+  - if  [[ -n "$BUILD_DOCS" ]]; then cargo doc --features docs; fi
+  - if  [[ -n "$BUILD_BOOK" ]]; then mdbook build docs && mdbook test -L ./target/debug/deps docs; fi