ftplugin/lua.vim: improve run buffer funcitonality.
ftplugin/css.vim: fix minor bug.
ftplugin/javascript.vim: fix minor bug.
ftplugin/javascript.vim: revert to using 'collapse' brace style.
ftplugin/html.vim: minor change.
ftplugin/javascript.vim: add buffer mapping `,,`.
vimrc: minor change.