Add PullRequest.ismerged() method with retry decorator
Add method to check whether PR base repo has issues enabled
Return empty list in get_labels()/get_comments() if issues are disabled
Fix test_pull_request unit tests
Add unit tests for get_labels/get_comments with issues disabled
Merge pull request #175 from sbesson/whitelisted_retry

Decorate GitRepository.is_whitelisted() with retry_on_errors
merge master -D org: PR 159 (Tag release prefix)
merge master -D org: PR 176 (Teach scc merge commands to work with repos without issues)
merge master -D org

Repository: openmicroscopy/snoopycrimecop
Already up-to-date.

Merged PRs:
  # PR 159 sbesson 'Tag release prefix'
  # PR 176 sbesson 'Teach scc merge commands to work with repos without issues'
Generated by SCC-merge#367 (http://ci.openmicroscopy.org/job/SCC-merge/367/)