Add ghe-rsync wrapper command, silence vanished file warnings
Use ghe-rsync wrapper command in all backup/restore commands
Filter vanished file warnings from both stdout and stderr

Versions of rsync before 3.0 wrote warnings to stdout. The behavior
was changed to write to stderr in 3.0 but we support versions going
back to 2.6.4.
Merge pull request #52 from github/fix-vanished-files-warnings

Fix vanished file warnings causing ES transfer to fail