See https://github.com/Node-SMB/marsaud-smb2/blob/7979fa0c1b362936caf2646bb19c70c4e2d842a7/lib/smb2.js#L7

The current implementation was broken (it did not always close dir handlers).

Removing this method also permit us to remove the following dependencies:
- Babel 5 (very old and unmaintained)
- Bluebird

- SMB method and params are injected
- synchronously created for better stack traces

Similar to 4b8f5754

Similar to 4b8f5754

`flag` option is also supported for `fs` compatibility

Test pre-condition can leads to race-conditions.
Also current code was hiding SMB error.

And fix `new Buffer()` uses.