Update brew formula opt shortcut.

Author: havenwood

homebrew/chruby.rb

@@ -14,7 +14,7 @@ def install
   def caveats; <<-EOS.undent
     Add the following to the ~/.bashrc or ~/.zshrc file:
 
-      source #{opt_prefix}/share/chruby/chruby.sh
+      source #{opt_share}/chruby/chruby.sh
 
     By default chruby will search for Rubies installed into /opt/rubies/ or
     ~/.rubies/. For non-standard installation locations, simply set the RUBIES
@@ -34,7 +34,7 @@ def caveats; <<-EOS.undent
     To enable auto-switching of Rubies specified by .ruby-version files,
     add the following to ~/.bashrc or ~/.zshrc:
 
-      source #{opt_prefix}/share/chruby/auto.sh
+      source #{opt_share}/chruby/auto.sh
     EOS
   end
 end