Fix user filter for users with dashes
Add beginning of implementation for tracking branches

- Create candidate_branches dictionary
- Add find_candidates_branches() method to list branches to merge
Add failing branch merging test to scc merge integration test

- Add push_branch() method to Sandbox test (called by open_pr)
- Refactor test_merge.py to have 2 test classes TestMergePullRequest and
TestMergeBranch
- Add simple TestMergeBranch.testMerge test
Add logic to add tracking branches remotes
Add first implementation of branch merging in merge() method

- Refactor the conflicting logic in local scope function safe_merge()
Fix branch merging logic
Improve formatting of commit message for merged/conflicting branches
Add simple check for mergeable status in find_candidates()

This commit prevent PRs with a non-mergeable state from entering the merging
pool of PRs and improves the specificity of the exclusion comment.
Fix flake8 warning
Fix --info message appending
Improve formatting of --info output for candidate branches
Fix scc to comply with PEP8 1.5.0
Merge pull request #154 from sbesson/pep8_1.5.0

Fix scc to comply with PEP8 1.5.0
Merge remote-tracking branch 'origin/master' into branch_tracking
Merge pull request #152 from sbesson/150_mergeable

Add simple check for mergeable status in find_candidates()
Merge pull request #153 from sbesson/branch_tracking

Add first implementation of branch tracking in `scc merge`
Revert "Add simple check for mergeable status in find_candidates()"

This reverts commit 920bb3718a2818bbf9ef86414d45ff343dd94076.
Merge pull request #155 from sbesson/non_mergeable_revert

Revert "Add simple check for mergeable status in find_candidates()"
Add comment for PullRequests with a description

When passing `--comment` to scc merge, Pull Request with no description
should be commented during the merge operation.
Flake8 the entire repository including setup.py