Needs error handling if `curl` calls fail

[william-richard]

Hi,

We've been using this package for a while, and noticed that it will not raise any errors of the github API calls fail.

This is especially difficult to address because the code ultimately shells out to curl - the --fail flag could be used, but then curl would not report the error message github encountered.

I think the best way to address this would be to switch from using curl to making the HTTP call in code, and then checking the error code.

Sadly, I don't really know javascript - I would be happy to help, but I'm not entirely sure how to implement even something as simple as an HTTP GET.