Solaris support

:construction: 
- [x] Works on 10.11 
- [ ] Works on 10.5
- [ ] Add new entries to $PATH only when the entries are not already present.
- [ ] WIP commits addressed

cc @schisamo @scotthain 
I would agree, but this is required to make it so things other than omnibus work. I believe @yzl ran into an external code dependency that needed this.