Add .no-sublime-package file

Tell Package Control to extract plugin files from .sublime-package to Packages  (fixes #9)

Apparently now fresh versions of Package Control for ST3 install plugins to Installed Packages as .sublime-package and way to force installation to Packages is to add .no-sublime-package file.
Ref: wbond/sublime_package_control#349
Thanks: csscomb/csscomb-for-sublime#5