Fix getting user's git name and email

see:
https://github.com/yeoman/generator/blob/ed0fa6842b2fac12b521e1902cc5a1d6cfcf6e1c/lib/actions/user.js#L24
https://github.com/yeoman/generator/blob/ed0fa6842b2fac12b521e1902cc5a1d6cfcf6e1c/lib/actions/user.js#L44