allow to unset a previously set RANGE value

... and add the unset_range_test.py unit test exercising it

Reported by: Zdeněk Pavlas
Bug: https://bugzilla.redhat.com/928370
allow to use setopt(..., None) as unsetopt()

... and extend the unset_range_test.py unit test to exercise it

Reported by: Zdeněk Pavlas
Bug: https://bugzilla.redhat.com/928370
Merge pull request #29 from kdudka/bz928370

[RFE] support setopt(pycurl.RANGE, None)
Add a test for bogus init flags and fix test name
Merge pull request #30 from p-push/global-ack-eintr

Global ack eintr
Python 3 support.

http://sourceforge.net/tracker/?func=detail&aid=2917775&group_id=28236&atid=392779
Corrected Python 3 support.

http://sourceforge.net/tracker/?func=detail&aid=3188495&group_id=28236&atid=392779
Python 3 compatibility: StringIO (src)
Python 3 compatibility: StringIO (examples)
Python 3 compatibility: xmlrpclib
Python 3 compatibility: urllib (src)
Merge pull request #31 from p-push/python-3-easy

Python 3 support
Correctly handle big timeout values

http://curl.haxx.se/mail/curlpython-2013-04/0000.html
Add support for CURLOPT_USERNAME / _PASSWORD

Original patch by Wim Lewis (https://sourceforge.net/u/wiml/profile/).

Original patch description:

This is a really trivial patch to add support for the CURLOPT_USERNAME and
CURLOPT_PASSWORD options (and their _PROXY equivalents), which affect
the same parts of libcurl's state that CURLOPT_USERPWD does but which
don't require you to combine the username and password into one string first.
(Libcurl just immediately parses it apart again anyway.)

I've tested against libcurl-7.21.0, and looked through the source for
libcurl 7.20.0 and 7.19.5 to verify that it looks like it should still do
the right things there (in particular that curl_easy_setopt(..., NULL)
does the reasonable thing with these options).

https://sourceforge.net/p/pycurl/patches/10/
Merge pull request #32 from p-push/curlopt-username

Add support for CURLOPT_USERNAME / _PASSWORD
Fixes invalid XHTML in documentation

doc/callbacks.html and doc/curlshareobject.html were not valid xhtml.

Thanks to Ivo Timmermans for the original report and patch to Ubuntu (LP: #364168)
Merge pull request #33 from p-push/doc-xhtml

Fixes invalid XHTML in documentation
Use nose test skipping functionality
Merge pull request #34 from p-push/nose-skip

Use nose test skipping functionality
Fix a tiny memory leak in util_curl_init()

Each time a new Curl object is created util_curl_init() leaked
a small string buffer. The attached patch fixes the leak --
curl_easy_setopt() strdup's its argument; the caller does not need
to keep the buffer around for it.

https://sourceforge.net/p/pycurl/patches/13/