Comparison operator negation rules can be incorrect

[alangpierce]

decaffeinate is producing the wrong JavaScript based on my CoffeeScript input:

unless NaN > 1
  console.log 'first'
else
  console.log 'second'

(repl)

I get this output:

if (NaN <= 1) {
  console.log('first');
} else {
  console.log('second');
}

Here's what I expect it to be instead:

if (!(NaN > 1)) {
  console.log('first');
} else {
  console.log('second');
}

This is causing at least two problems in atom. I think this negation behavior probably needs to be behind a --loose flag, since it doesn't work for operands like NaN and undefined.