Password is stored in plain text when authenticating

[Olivia5k]

https://github.com/sigma/gh.el/blob/master/gh-auth.el#L63-L73

Does this have to happen? It seems pointless since we are storing the access token at the same time.

Originally noted in https://github.com/defunkt/gist.el/issues/84.

[sigma]

fixed in commit 2d7221d