Use consistent markdown for all code examples

[stomar]

Some code examples are defined using the {{ highlight xy }} tag in the markdown files, some are defined using code blocks with attribute lists, like {: .code .bash-code}, some are defined as plain code blocks. This results in differently structured html.

Consistent syntax would simplify the CSS.

[stomar]

Examples:

1. highlighted: home page, Ruby in 20 minutes
2. attribute list: libraries page
3. plain code block: about page (-> no css style)

[stomar]

I'm experimenting with converting all Ruby/Bash code blocks to Jekyll highlighted code blocks during the import task (by using the existing CSS classes). For non-highlighted code blocks {: .code} should be used.

[stomar]

Closed with 6f429c9.

Use attribute {: .code} for "generic" code (like output, mailing list subscription command), else use the highlight tag, specifying the language.