switch 'retry' with callback so callback is last arg

[seanrose]

When I integrated the version with retry logic added, it broke the blocking package broadcast is using – it turns out that the package has a hard assumption that the callback of any function is always the final argument. A little digging around leads me to believe that always having the callback as the last arg is standard convention.

I can update the tests and everything also, but just wanted to make sure you're cool with this before submitting a PR…

[lakenen]

I think I'll actually rework the arguments a bit so that every method accepts zero, one or two args: ([opt], [cb]).

So then it will become something like:

client.documents.get({ id: 'someid', retry: true }, function (err, response) {
  // stuff
});

Or with other options, e.g.:

var options = {
  id: 'someid',
  retry: true,
  params: { is_downloadable: true }
};
client.sessions.create(options, function (err, response) {
  // stuff
});

// but, still keep the shorthand with just the id:
client.sessions.create('someid', function (err, response) {
  // stuff
});

Thoughts?

I totally agree that having the trailing retry is nonstandard and weird...

[lakenen]

Or maybe, to be more correct, only the actual options would be options, so in the case of sessions (since id is not optional):

var options = {
  retry: true,
  params: { is_downloadable: true }
};
client.sessions.create('someid', options, function (err, response) {
  // stuff
});