Mark required Rust version as 1.29

690b3f9 updated the required version in Cargo.lock and in the CI config files, but not in the installation instructions.

docs/content/documentation/getting-started/installation.md

@@ -47,7 +47,7 @@ $ choco install zola
 ```
 
 ## From source
-To build it from source, you will need to have Git, [Rust (at least 1.28) and Cargo](https://www.rust-lang.org/)
+To build it from source, you will need to have Git, [Rust (at least 1.29) and Cargo](https://www.rust-lang.org/)
 installed. You will also need additional dependencies to compile [libsass](https://github.com/sass/libsass):
 
 - OSX, Linux and other Unix: `make` (`gmake` on BSDs), `g++`, `libssl-dev`