Ignore mustache helpers inside code blocks

When documenting Stache or Mustache helpers you currently have to put a `\` in front of them in order for the builder to try to process them. This is true even inside code blocks.

```
// Use the calendar helper to insert a calendar with this syntax:
\{{calendar}}
```

This is problematic for using README.md as the main API page or home page (as brought up in #155) because on Github, the README would show the backslashes.

Ignoring helpers inside code blocks would probably be the best solution to this.

This should also be documented. Probably somewhere in here: http://localhost:8080/docs/documentjs.generators.html.html
It won't matter if it's buried since it's a niche use case.

Start by reproducing the README.md example and tracing how the builder processes helpers inside fenced code blocks. Check the documentation at documentjs.generators.html.html for the appropriate place to describe the behavior. Done means mustache helpers in code blocks render without backslashes, while the behavior is documented.

Written by the indexing model from the issue text.