use standard markup validator instead of validator.nu to check HTML4 and
XHTML documents
Added dir doc/ for doc & presentations.

Added v0.1 of an outline for a presentation.
Some ideas added to the presentation script
Added directory tree to explain the architecture.
Added details about dependencies.
fix service url + query parameter name
fix GET/POST request to markup validator
Merge pull request #50 from w3c/denis/markup-validator-html4-xhtml

use standard markup validator instead of validator.nu to check HTML4 and HTML documents
compound document: 1st version getting the content-type of each document
and filtering only the html/xml
2nd version without checking the content-type because it's too slow
clean up
forgot 'done()' at the end of the rule
Validation: s/checkbox/select box/ to offer the options 'no validation',
'simple validation' and 'recursive validation'
fix tests
add recursive validation for compound documents