Update to reflect Sublime Text 3 support and different OSes

The plugin has been tested with Sublime Text 2 and 3, using FileZilla
3.7.4.1, on Windows 7, OS X 10.9.1 and Ubuntu Linux 13.10.
Merge pull request #7 from vallovic/master

Update to reflect Sublime Text 3 support, different OSes and sitemanager.xml not found