Build in support for brailleR

[hadley]

Need to add this to the appropriate place in plot/print methods:

if (is_installed("BrailleR") && isTRUE(getOption("BrailleR.VI")) {  
  BrailleR::VI(graph)
}

[yutannihilation]

This looks a good idea to me, but brailleR was removed from CRAN last year, so this issue needs to wait for the return.

Related discussion: #4256

[hadley]

Rather than waiting we can use some hack to prevent CRAN seeing the ::; then it'll work when BrailleR returns.

[yutannihilation]

I see.

[thomasp85]

Is the output of BrailleR::VI() meant to be returned or should it just be printed?

[hadley]

Just printed