Prefer R.inc and R.dec over R.add by 1 or -1

[lo1tuma]

This should be a warning:

R.add(1) // could be written as R.inc
R.add(-1) // could be written as R.dec

[davidchambers]

R.subtract(1) is not equivalent to R.dec. Instead, we want:

• R.add(1) better written R.inc; and
• R.add(-1) better written R.dec.

[lo1tuma]

@davidchambers Good catch, thanks. I‘ve updated the description.

[gilligan]

Oops, thanks @davidchambers - that happens when I make up stuff on a blackboard :)