Upgraded package to Sublime Text 3

Made the necessary changes to make the package work for Sublime Text 3. Tried to make the impact of the changes as small as possible, only the absolute necessary to make it work in version 3 while ensuring compatibility with version 2. The following actions has been done:
* Language changes for Python 3.3
* Code refactoring due to changes to Sublime API accoring to http://www.sublimetext.com/docs/3/porting_guide.html. Mainly due to restriced access to sublime api during startup and unavailablity of begin_edit/end_edit

The changes was tested on Sublime Text 2 (2.0.1 and 2.0.2) and Sublime Text 3 beta (build 3047).