updated:Highlight trailing spaces in our editors (vim, emacs, ..)

[Bao, Zheng]

When the trailing spaces are highlighted, it is easy for us to delete it
and don't create new trailing spaces.

Zheng

Vim:
Add following lines in the .vimrc
"The highlight way can be in your own way.
Highlight ExtraWhitespace ctermfg=DarkGray ctermbg=yellow 
"Show trailing whitespace
match ExtraWhitespace /\s+$/

Emacs:
Add the following lines into the .emacs
(setq-default show-trailing-whitespace 1)