vim : Converting tabs to spaces

http://vim.wikia.com/wiki/Converting_tabs_to_spaces
http://superuser.com/questions/632657/how-to-setup-vim-to-edit-both-makefile-and-normal-code-files
http://stackoverflow.com/questions/8999208/quickest-way-to-revert-spaces-to-tabs-in-vim

:set tabstop=4
:set shiftwidth=4
:set expandtab

[Note] set to ~/.vimrc
[Note] autocmd FileType make set noexpandtab