symlink override

this fixes the Issue #260.
https://github.com/spf13/spf13-vim/issues/260

If a old symlink of .vimrc exists the new symlink is created by force.
Merge pull request #261 from sanitoeter/3.0

symlink override
replace vim-powerline with beta one, remove tabular, php, ruby, twig, add
plugins for SQL, jquery and Development
Merge remote-tracking branch 'upstream/3.0' into cfml