Attempt ReadTheDocs.org bug fix

ReadTheDocs seems to be unable to import __winreg which likely means the
import is not occurring on a Windows machine. The mercurial repository
invokes the same import. The current github version of dragonfly does not
import win32gui, so attempting to use dragonfly 0.6.6b1 in the
requirements file.

requirements.txt

@@ -1 +1 @@
--e hg+http://pywin32.hg.sourceforge.net/hgweb/pywin32/pywin32/#egg=pywin32
+-e git+http://github.com/t4ngo/dragonfly/#egg=dragonfly