Add pygments stylesheet for example code

[postmodern]

Need to find a pygments stylesheet that closely matches the colour scheme used on http://www.ruby-lang.org/en/

[stomar]

I'm working on adapting the default pygments stylesheet. Any spontaneous thought about where/how to integrate it? At the moment, syntax highlighting styles are defined in high.css and print.css.

[postmodern]

Kicking ass 😎

Should probably overwrite high.css, and include it using the same trick as with the examples.js file.

[stomar]

I thought about a dedicated pygments.css file and including that in screen.css (and removing syntax styles from high.css).

[stomar]

Afterthought: must the random code examples and the code snippets on pages like the "Ruby in 20 minutes" tutorial be treated differently?

[stomar]

Mostly done. Open:

• consider whether an even more reduced color scheme should be used for the home page examples
• not all colors have been validated due to missing examples for some syntax elements

[stomar]

I made some colors brighter for better contrast, see 0abfa5b.
And I think there's no harm in using the same colors for the home page examples.