Flexible binary path search

Hi,
I created a gem for the linux wkhtmltoimage binaries as seen for wkhtmltopdf.

To use it I also needed to change the path selection in IMGKit. This goes along with PDFKit too. It also keeps compatible with the normal way as it is now.

Since I guess this is useful for others too I'd love to see this merged and the gem updated at rubygem.org.

Thanks in advance for response.


wkhtmltoimage-binary gem:
https://rubygems.org/gems/wkhtmltoimage-binary