Go-github: Support preview project card details from Issue Events API

[gmlewis]

GitHub Developer API announcement:
https://developer.github.com/changes/2018-09-05-project-card-events/

This would be a great PR for any new contributor to this repo or a new Go developer.
All contributions are greatly appreciated!

Feel free to volunteer for any issue and the issue can be assigned to you so that others don't attempt to duplicate the work.

Please check out our CONTRIBUTING.md guide to get started.

Thank you!

Edit: Woohoo! Issue #1000! :smile:

[Charliekenney23]

I can take this!

[psdh]

Heya! @Charlieksenney23 , are you still working on this?

If not, I'd love to take a stab! :dagger: :smile:

[Charliekenney23]

@psdh Sorry I got caught up with something, feel free to take it!

[palash25]

Hey @psdh are you still working on it? If not then I would like to give it a try

[palash25]

I don't see a PR referencing this issue it seems to have been abandoned by the original claimer. @gmlewis can I be assigned to this?

[gmlewis]

Thank you, @palash25!
I can't send you an invite, but maybe @willnorris can.
In the meantime, please consider this issue assigned to you.

[willnorris]

@palash25 invite sent.