Support for other systems

[mbojan]

Have a look at https://github.com/mbojan/clipboard and write_cb(). I may be able to submit a PR next week or so if you are interested.

[MilesMcBain]

https://github.com/mdlincoln/clipr can provide a drop-in replacement for clipboard() that works on all platforms. It's on CRAN too which is nice.