Use mdbook master branch until 0.1.8 releases

Author: AndyGauge

README.md

@@ -21,7 +21,7 @@ If you'd like to read it locally:
 ```bash
 $ git clone https://github.com/rust-lang-nursery/rust-cookbook
 $ cd rust-cookbook
-$ cargo install mdbook --vers "0.1.7"
+$ cargo install mdbook --git https://github.com/rust-lang-nursery/mdBook
 $ mdbook serve --open
 ```
 

ci/install_deps.sh

@@ -16,8 +16,7 @@ if [[ "${CONTENT_TESTS:-}" == 1 ]]; then
         pyenv global system 3.6
         pip3 install --user link-checker==0.1.0
     fi
-    cargo install mdbook --vers '0.1.7' --debug
+    cargo install mdbook --git https://github.com/rust-lang-nursery/mdBook --debug
 fi
 
 exit 0
-