install wkhtmltopdf and xvfb
add chef recipe to install wkhtmltopdf (static)
add test for wkhtmltopdf
fix wkhtmltopdf documentation in README
cleanup the wkhtmltopdf recipe
Merge branch 'wkhtmltopdf' of git://github.com/Dextro/sneakers into Dextro-wkhtmltopdf

Conflicts:
	README.md
[chef extra::wkhtmltopdf] adds checksums
Merge branch 'Dextro-wkhtmltopdf'