Fixes for ST3 compatibility

Hi, I made some changes to make this plugin support Sublime Text 3. They were pretty minimal: parentheses for one print statement and some by-the-book changes according to http://www.sublimetext.com/docs/3/porting_guide.html (see the section Restricted begin_edit() and end_edit()).

I suspect the latter will break compatibility with ST2, so you might want to make an ST3 branch.