Fix for named params
Don't run shell command for operating_system every time
Brew basics

Can update, search, install, remove, and #installed?
Can install a specific brew version
Converted to new return design
Converted back to use @internal_pwd

Keeps from altering ENV['PWD'] when not using as an active live shell.
Refactored package manager
Use package manager based on OS
Can install by version now
Refactored shells