Remove unused code from log.py
Add pywin32 as dependency in setup.py

This omission was reported by Muelli in issue #4. Even though the core
of Dragonfly is not operating specific, it does rely on Win32 functions
for interfacing with the backend speech recognition engines, for
executing e.g. keyboard and mouse actions, etc. In its current state it
therefore does require pywin32 to operate.

I added pywin32 to the install_requires argument of the setup() function.
This will give an error during installation if that package is not
present on a system. It does not automatically install it, because
pywin32 isn't available via PyPI. On my test systems the presence of
pywin32 is detected correctly after manually installing it.

Resolves #4.