Support for mulitple backends

Also:

• Call signatures of notify() methods cleaned up
• Generic way of passing options specific to backends

Nicer duration formating for `ntfy done` and python wheels!

v0.2.1

support universal wheels

Better native notifications!

Linux notifications switched to use dbus and windows pulls in pywin32 by using pypiwin32 on pypi.

PyPi docs only update

Switched to RST so that PyPi looks prettier: https://pypi.python.org/pypi/ntfy

Windows and MacOS support!

Added native desktop notification support for Windows and Mac OS X environments.

1st tagged release! Pex packaged script! linux desktop notifications!

ntfy.zip contains pex packaged python script. The only dependency is that python is installed. This should work out of the box on Mac OS X and most Linux distributions.