You should npm install -g purescript, not npm install -g purs. The latest purs version in npm is 0.12.5 (and it fails to install with my npm). Maybe it should be removed / updated @JordanMartinez?
BTW, I just checked: The Getting Started Guide in the doco does say “npm install -g purescript”, so it was a very coincidental Freudian mistake that I typed “npm install -g purs” and thought it were correct…