adding more flexible *nix system support

Not all systems have su and bash in /bin. This change should allow for a bit more flexibility across different *nix styles. 

I also would love to see this tagged as 1.0, but git/github doesn't support adding tags to a pull request. 

**To tag this sha:**
```$ git checkout #{this sha}```
```$ git tag -a 1.0.0```
```$ git push --tags```