Added mini-dir option to POWERBASH_PATH

Added 'mini-dir' option

```
 ~ $  POWERBASH_PATH=mini-dir
 ~ $  mkdir -p /tmp/test/foo/bar/moo/cow
 ~ $  cd /tmp/test/foo/bar/moo/cow
 /t/t/f/b/m/cow  $  mkdir -p ~/tmp/foo
 /t/t/f/b/m/cow  $  cd ~/tmp/foo
 ~/t/foo  $  
```