For those that just want to get to the point and start watching.
brew install streamlink && brew cask install vlc &&
  git clone https://gist.github.com/Jahhein/f96574f45b24aa797af13ce4c6812076 twitch-streamlink &&
  cd twitch-streamlink &&
  chmod 755 twitch.sh  &&
  ./twitch.shThe package Livestreamer was depcricated when I first authored this. A new fork of Livestream was created named Streamlink therefore I have updated all information to get up and running with Streamlink and a GUI if the command line makes your uneasy/confused.
brew install streamlink && brew cask install vlcThe GUI is just like any application, but requires streamlink package to still be installed.
OPTIONAL: brew cask install streamlink-twitch-gui for the GUI.
- $1 is the stream name on twitch.tv
 - $2 is the stream quality - audio, low, medium, high, best, or specific like I mention below.
 
Examples usages
twitch.sh twitchpresents best # best video quality available
  
twitch.sh lirik 900p60        # 900p60 quality
  
twitch.sh monstercat audio    # only stream audio
twitch.sh kitboga 480p        # 480p qualityPlease report any issues you come across! Thank you!