Push fails because github is more strict now. #12

From email:

Then, the problem appears in js-github/mixins/github-db.js , the function " encodeDate(date) ", it's a very small mistake ,but when the true date is " 2004-05-03T17:30:08+08:00" ,the result of your program is "2004-05-03T17:30:08+0-8:00" ,with a extra "-" . With the problem , when sending a "commit" to github, the response will replay "422" error .