Make html5check.py send a User-Agent header
Make html5check.py send a User-Agent header

Fixes #434 Thanks @gilleslamiral

validator/validator,takenspc/validator,takenspc/validator,takenspc/validator,validator/validator,tripu/validator,tripu/validator,validator/validator,validator/validator,takenspc/validator,tripu/validator,validator/validator,tripu/validator,tripu/validator,takenspc/validator