Add support for new Admin endpoints and attributes (Closes: #196)

[thewheat]

Fixes: #196

Added

• ability to read more attributes:
  • away mode enabled
  • away mode reassignment
  • team_ids (for admins)
  • admin_ids (for teammates)
  • avatar
• tests for
  • listing all admins
  • viewing an admin
  • viewing a team
• ability to view admin by id
• ability to set away mode and reassignment

[choran]

Do you think we need a quick test for the find?
Just wanted to check if you think this is needed or not

[choran]

Yo Tim,
I looked over this. Firstly, I did not realise there was so little functionality for the admin endpoint in the Java SDK For example. I saw you added find functionality, I did not realise that was missing here. So it is great to have that.

I think it needs a readme update with some simple examples since you are adding the setting and finding options. If you have those handy it might be good to add them. I can merge it then. Alternatively if you dont have time we can merge it now and I can add readme examples later?

The only comment was whether we needed a find test as well.
Lots of great stuff here, nice work @thewheat

[thewheat]

@choran definitely agree with respect to the readme. If you're looking to do a release soon I think we should merge and add examples later.

With regards to the tests on find. I don't think we do any testing for find operations in this SDK yet. Should we just look at the requests it makes and verify that it is properly formed e.g. when Admin.find("1234") is called and ensure a request to https://api.intercom.io/admins/1234 is made?

[thewheat]

@choran updated readme 👍

[choran]

👍