Use sw=2 when editing *.rb.

.vim/vimrc

@@ -93,6 +93,7 @@ au BufNewFile,BufRead *.sls set filetype=yaml
 au BufNewFile,BufRead *.sls set shiftwidth=2
 au BufNewFile,BufRead *.mk set noexpandtab
 au BufNewFile,BufRead *.psgi setf perl
+au BufNewFile,BufRead *.rb set shiftwidth=2
 au BufNewFile,BufRead Makefile set noexpandtab
 au BufReadPost * if line("'\"") > 0|if line("'\"") <= line("$")|exe("norm '\"")|else|exe "norm $"|endif|endif
 autocmd BufEnter * silent! lcd %:p:h