Fix spelling in install/osx.rst

Author: campbellr

docs/starting/install/osx.rst

@@ -35,7 +35,7 @@ simply run
 
     $ /usr/bin/ruby -e "$(/usr/bin/curl -fsSL https://raw.github.com/mxcl/homebrew/master/Library/Contributions/install_homebrew.rb)"
 
-Then, insert the Homebrew directory at the top of your ``PATH`` enviornment
+Then, insert the Homebrew directory at the top of your ``PATH`` environment
 variable. You can do this by adding the following line at the bottom of your
 ``~/.bashrc`` file