Change normalized callback arguments.

After this commit the callbacks for the write functions are as follows.

```
db.users.insert(document, callback);    // => callback(err, [document])
db.users.save(document, callback);  // => callback(err, document)
db.users.update({ ... }, { ... }, callback); // => callback(err, lastErrorObject)
db.users.remove({ ... }, callback); // => callback(err, {n: amountRemoved})
db.users.findAndModify({ query: { ... }, update: { ... }}, callback); // => callback(err, document, lastErrorObject)
```

The reason for these changes is that sometimes you might want to save a document and retrieve the
ObjectId it was saved with.

The problem of `save` returning '1' when the operation was an update is solved
here, and a test case was added for this as well.

index.js

@@ -37,12 +37,6 @@ var getCallback = function(args) {
 	return typeof callback === 'function' ? callback : noop;
 };
 
-var truncateCallback = function(callback) {
-	return function(err) {
-		callback(err);
-	};
-};
-
 // Proxy for the native cursor prototype that normalizes method names and
 // arguments to fit the mongo shell.
 
@@ -196,13 +190,19 @@ Collection.prototype.remove = function() {
 	this._apply(DRIVER_COLLECTION_PROTO.remove, arguments.length === 0 ? [{}, noop] : replaceCallback(arguments, callback));
 };
 
-Collection.prototype.insert = function() {
-	var callback = truncateCallback(getCallback(arguments));
-	this._apply(DRIVER_COLLECTION_PROTO.insert, replaceCallback(arguments, callback));
-};
-
 Collection.prototype.save = function() {
-	var callback = truncateCallback(getCallback(arguments));
+	var self = this;
+	var args = arguments;
+	var fn = getCallback(arguments);
+
+	var callback = function(err, doc) {
+		if (err) return fn(err);
+		if (doc === 1) {
+			fn(err, args[0]);
+		} else {
+			fn(err, doc);
+		}
+	}
 	this._apply(DRIVER_COLLECTION_PROTO.save, replaceCallback(arguments, callback));
 };
 

tests/test-insert.js

@@ -0,0 +1,10 @@
+var assert = require('assert');
+var mongojs = require('../index');
+var db = mongojs('test', ['a','b']);
+
+db.a.insert([{name: "Squirtle"}, {name: "Charmander"}, {name: "Bulbasaur"}], function(err, docs) {
+	assert.ok(docs[0]._id);
+	assert.ok(docs[1]._id);
+	assert.ok(docs[2]._id);
+	db.close();
+});

tests/test-save.js

@@ -0,0 +1,17 @@
+var assert = require('assert');
+var mongojs = require('../index');
+var db = mongojs('test', ['a','b']);
+
+db.a.save({hello: "world"}, function(err, doc) {
+	assert.equal(doc.hello, "world");
+	assert.ok(doc._id);
+
+	doc.hello = "verden";
+	db.a.save(doc, function(err, doc) {
+		assert.ok(doc._id);
+		assert.equal(doc.hello, "verden")
+		db.a.remove(function() {
+			db.close();
+		});
+	});
+});

tests/test-update-and-callback.js

@@ -14,4 +14,4 @@ insert([{
 		done();
 	});
 	sync = false;
-});
+});