refactored examples to own class
support options in examples
let hooks return the updated string instead of replacing it
use hook to remove highlight markers
highlight code as option
renamed options to filters
extracted filtes into new file; allow default filters
added tests for highlights filter; refactored tests
allow filternames in underscore and dash case
renamed layout-example and refactored into full-width filter
automatically unindent test cases
moved haml-examples into filter
moved javascript-examples into filter
optimized regexp