Fix rendering of code block

Also add $ to tell input from output
Bugfix: code block not rendering in 02-func
Bugfix: code blocks not rendering in novice/python/03-loop
Bugfix: code block not rendering in novice/python/04-cond
Merge pull request #501 from zonca/formatting_fixes

Bugfix: fix rendering of code block
Refer to rescale() instead of center()
Refer to rescale() instead of normalize()
Merge pull request #522 from DamienIrving/small_fixes

Fixed typos in Creating Functions lesson
Merge remote-tracking branch 'upstream/master'

getting up to speed with bc master