pass back entire response from github in case of error

current behavior conceals valuable information, e.g. 

```
$ node test.js 
Your GitHub username: maxogden
Your GitHub password: ✔✔✔

Your GitHub OTP/2FA Code (optional): 999999
[Error: Validation Failed]
```

this PR changes it to this:

```
$ node test.js 
Your GitHub username: maxogden
Your GitHub password: ✔✔✔

Your GitHub OTP/2FA Code (optional): 999999
[Error: {"message":"Validation Failed","documentation_url":"https://developer.github.com/v3/oauth_authorizations/#create-a-new-authorization","errors":[{"resource":"OauthAccess","code":"already_exists","field":"description"}]}]
```

in this case the problem was that I guess github has a unique constraint on the app `description` field and it wants me to change it?