Use the Github API v3 because the email call has changed.

This solves the error message _```Coding error detected, it must be fixed by a programmer: clean_param() can not process objects, please use clean_param_array() instead.```_, caused by an email object is received instead of a string.

Old API return value:
```json
["foo@bar", "foobar@gmail.com"]
```

New return value:
```json
[
    {"email": "foo@bar", "verified": false, "primary": true},
    {"email": "foo@bar.com", "verified": true, "primary": false},
]
```

> _See https://developer.github.com/v3/users/emails/#list-email-addresses-for-a-user_

This patch get the first verified email from github email list, otherwise the useremail will be a not verified empty string.