QGIS-2.x support

Thanks for #6 merging!
I added not only QGIS-1.8 but also QGIS-2.x support.
And I confirmed that all functions work correctly on the following environment.
- QGIS-1.8/1.9dev on Windows 7 OSGeo4W 32bit (Last update at 2013/07/19)
- QGIS-2.0.1 on MacOSX MacPorts

Regards,