parse empty form data

Fixes #162
In this case there is a single delimiter which is both starting
and ending boundary.
Merge pull request #224 from egirshov/issue-162

parse empty form data
do not pause request on error
Merge pull request #228 from egirshov/issue-69

do not pause request on error
Support upper case in file extensions.

Fixes felixge/node-formidable#233
Merge pull request #234 from vilcans/master

Support upper case in file extensions
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