fix issue #13 clean-git does not have a --dry-run option anymore
Borja (approved)
Branch: borlafu/svn-migration-scripts:issue-13-clean-git-documentation
Branch: atlassian/svn-migration-scripts:master
Open
Small documentation update: https://bitbucket.org/atlassian/svn-migration-scripts/issues/13/clean-git-does-not-have-a-dry-run-option