trim trailing whitespace in perlbrew_list

[shawnlaffan]

perlbrew list on my local system returns values with trailing spaces. These need to be cleaned up or they later get in the way of setting the local lib, and probably other functions.

Assuming the minimum R version exceeds 3.2.0 this could also use the trimws() function here:

perlbrewr/R/perlbrew.R

Line 70 in 3311841

gsub(pattern = "^(\\*| ) ", replacement = "")

I can generate a PR if needed.

Edit: Actually, it probably needs to be in a couple of places to handle the active item.