DL-29: The merge PR script should delete branches once the PR are merged
DL-29: The merge PR script should delete branches once the PR are merged

Author: Sijie Guo <sijieg@twitter.com>

Reviewers: Franck Cuny <franck.cuny@gmail.com>

Closes #24 from sijie/sijie/fix_merge_script

twitter/distributedlog,twitter/distributedlog,twitter/distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog,twitter/distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog,sijie/incubator-distributedlog,twitter/distributedlog