generate resume pdf using wkhtmltopdf package instead

Uses [wkhtmltopdf](https://www.npmjs.org/package/wkhtmltopdf) node package to do the PDF generation instead. This means wkhtmltopdf has to be present on the system in order to do pdf publishing. BizCaus from the freenode channel suggested theme styles optimized for print media (so users can choose the full or optimized version, as currently the pdf's are more pages than they should be due to gratuitous spacing). 

Note: I'm not sure about other systems but on Ubuntu 12.04 the wkhtmltopdf package was severely outdated and the CSS styles were not being rendered in the PDF. I'm not sure what version of wkhtmltopdf this was fixed in but I tested the latest version [here](http://wkhtmltopdf.org/downloads.html) and it worked well.
Maybe it's better to set the version number instead? To avoid things breaking up if/when the API changes.