option to call xclip or arbitrary programs with the url

[lolisamurai]

since I'm already calling a bunch of other external commands, might as well offer the option to call xclip or an arbitrary program with the URL and other params so people without a clipboard daemon can still get the url copied to the clipboard

[Kasia]

I'd love this one to be implemented, could try PRing something myself, but should I make it a command line option or something similar?
Also, should copying method be hardcoded to copy the url or should we give user an ability to select the method of copying? I guess we can try running either xsel --clipboard or xclip -selection c.