Added support for fetching what teams are part of this team.

[alexanderkjall]

Description

The call is to this endpoint https://developer.github.com/v3/teams/#list-child-teams-legacy

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[alexanderkjall]

I tried following the setup guide for writing tests, but without success, I got:

org.kohsuke.github.GHFileNotFoundException: http://localhost:35361/orgs/hub4j-test-org/teams/dummy-team {"message":"Not Found","documentation_url":"https://developer.github.com/v3/teams/#get-team-by-name"}

And didn't really understand why that happened.

[bitwiseman]

@alexanderkjall
Please add a test. I can then help you refine it.

[bitwiseman]

Also, please describe the steps you followed from the guide and the result from each step.

[alexanderkjall]

The problem that I had was due to not being a part of the test organization, once I was added it worked without problem.

[bitwiseman]

@alexanderkjall
I removed getChildTeams() - it is extremely easy to call listChildTeams().toSet(). If you feel strongly otherwise, we can add it to the next release.