[Tip]make vim copy and paste string with global clipboard.

First, we should make sure vim support clipboard feature by:

vim --version

We will see "+clipboard" if it support global clipboard.
Otherwise, we should install this debian package "vim-gnome" to make vim support global clipboard.

After we get global-clipboard-enabled vim, we should modify "~/.vimrc" and add this line:

set clipboard=unnamed

Then vim will copy and paste string with global clipboard.