* minor bugs fixed
* more bugs fixed.
* bug iterator-recursion-test.js max stack exceed.
+ local setImmediate to prevent no setimmediate polyfill on old node
- comments the debug code
typo
* [bug] can not test sync for db closed.
* [bug] the leveldown arugment is a 'class' so using leveldown.prototype to check whether sync methods exists
* update readme