Integrated: 674: Allow reviewers command in PR body

[Erik Helin]

Hi all,

please review this pull request that allows the `/reviewers` pull request command to be used in the PR body.

Testing:
- `make test` passes on Linux x64
- Added one additional unit test

Thanks,
Erik

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Commit messages:
 - 674

Changes: https://git.openjdk.java.net/skara/pull/823/files
 Webrev: https://webrevs.openjdk.java.net/?repo=skara&pr=823&range=00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-674
  Stats: 35 lines in 2 files changed: 35 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/skara/pull/823.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/823/head:pull/823

PR: https://git.openjdk.java.net/skara/pull/823