Update incoming_form.js

According to the document, it support hash options.
Merge pull request #242 from mashihua/patch-2

Support hash algorithm
skip empty buffers

This is a workaround for a #5715 in joyent/node
Merge pull request #244 from egirshov/issue-243

Fix #243: skip empty buffers
Update incoming_form.js

Important! Fixed running files handles for octet-stream parser.
Merge pull request #259 from simak-alexandr/patch-1

Update incoming_form.js
Typo in Readme.md - an changed to and
Merge pull request #265 from swr/master

Typo in Readme.md - an changed to and
added note about how it is integrated with Express
Merge pull request #266 from headwinds/expressNote

added note about how it is integrated with Express