Make async.transform actually support 2 arguments

The documentation suggests that both the `accumulator` and `callback` arguments to transform is optional. 

However, if both are left out (and transform therefore is called with only 2 arguments), transform crashes with a `iteratee is not a function` exception. 
This fixes that.

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/transform.js b/lib/transform.js
index 5d1342a..f001c51 100644
--- a/lib/transform.js
+++ b/lib/transform.js
@@ -50,7 +50,7 @@ import once from './internal/once';
  * })
  */
 export default function transform (coll, accumulator, iteratee, callback) {
-    if (arguments.length === 3) {
+    if (arguments.length <= 3) {
         callback = iteratee;
         iteratee = accumulator;
         accumulator = isArray(coll) ? [] : {};