Avoid parsing inline equations in code blocks

[bytesnake]

At the moment this code snippets

user@computer:~/rust-ml/book$ cd code/
user@computer:~/rust-ml/book/code$ cargo run --release --example kmeans

is parsed with the dollar symbols as inline equations.

[quietlychris]

There's now a native option for MathJax support in mdbook, by adding mathjax-support = true under the [output.html] heading, which might be a fair alternative to using the mdbook-scientific package as a pre-processor. I've experimented around with it a little for the update I'm putting together for the first couple of chapters now that Lifna 0.6 has come out. We'd also need to think about the gnuplot function that was being tested out.

https://rust-lang.github.io/mdBook/format/mathjax.html?highlight=mathjax#mathjax-support