resolve #261, explain args to callback to #del

[bewest]

Per bug report, example crafted from test.

Howdy, thanks for your work. I was reviewing a bunch of code, and noticed this note and thought it was easy enough.

[rvagg]

example has a few problems:

• callback function is named, this is not consistent with the rest of the examples (naming functions is good practice but we should be consistent, either name everything or nothing)
• callback content doesn't account for the non error case, it just assumes there will always be an error
• example needs to be somewhat real-world-ish, meaning that it shouldn't console.* and also throw is rarely going to be the way people deal with errors, it's much better to just have something like:

if (err)
  // deal with error

[rvagg]

Nice, I'm going to assume that since this is just a simple doc fix that nobody else is going to object so I'll merge. Thanks!