Enhancedment: use thread.Thread to execute util.file.determine_syntax_files
Enhancedment: use thread.Thread to execute util.file.determine_syntax_files

It seems that sublime.set_timeout_async still slow down the start up of
Sublime Text. For instance, the quick panel is not ready until a few second
after ST opens. I suspect that they share the same second thread.

Changing `sublime.set_timeout_async` to `threading.Thread` so that the quick panel
(and other UI) does not have to wait for util.file.determine_syntax_files

stoivo/GitSavvy,asfaltboy/GitSavvy,ddevlin/GitSavvy,stoivo/GitSavvy,asfaltboy/GitSavvy,ddevlin/GitSavvy,stoivo/GitSavvy,divmain/GitSavvy,divmain/GitSavvy,divmain/GitSavvy,ddevlin/GitSavvy,asfaltboy/GitSavvy