Implement compileOnSave, compile command, [per project] settings file

Implement compileOnSave, "compile" command, settings files and per project settings file.
Should fix #18

I have been greatly inspired by code from https://github.com/aponxi/sublime-better-coffeescript
I added him in the Thanks list, because 90% of the code comes from Sublime-better-coffeescript.

I am getting error about this line...

    Writing file /Users/billy/Desktop/delme.styl with encoding UTF-8
    Compiling on save...
    Traceback (most recent call last):
      File "./sublime_plugin.py", line 362, in run_
      File "./Stylus.py", line 93, in run
    AttributeError: 'Window' object has no attribute 'project_file_name'