Merge pull request #20 from Arcterus/master

Make the Homebrew paths more portable and improve the help menu
Use which to detect OS type
Use comand -v instead of which
Merge pull request #22 from Arcterus/master

Stop OS type warnings on Macs
Add some comments about $OSTYPE. See also #22
Use command -v only for brew
Merge pull request #21 from 10sr/which

Use which to detect OS type