a few fixes in a row

* fixed `grep: invalid max count`
    - manning-up.sh had an error making grep for title fail
* add output of file being processed
    - some output about which file gets processed by ronn, makes debugging easier
* add missing hashbang
    - there was the hashbang missing in `bin/git-obliterate`
* remove /usr/bin/env from hashbang
    - hashbang should not call shell-interpreter using env
* fix complains from `checkbashism -px`
    - some scripts used bashisms, but relied on /bin/sh
    - /bin/sh neccessarily not needs to be symlinked to /bin/bash