Automatically detect dotfiles directory.So we can do something quickly.
For example,we can use `eg' to edit gitconfig file,then `.g' to load the config.
All these edit will take effect in the dotfiles git repo directory.
1.Add vim modeline for git config file.
2.Add a file which called 'install_tools.sh' to automatically install some essential commane line tools
	when I changed to a new environment.