Fixed indent_size issue when using tabs.

I was having the issue that I couldn't get it to work with `indent_style = tab`. My Atom is default to soft tabs 2 and was trying to do hard tabs 4 in editorconfig by setting `indent_style = tab` and `indent_size = 4` with no luck as my Atom default was two and the package is only setting indent_size for spaces. This change is what is working for me but not sure if there is a better or more preferred way.