Installation instructions for rdkit on Mac added

Author: faribas

documentation/source/users/rmg/installation/QMthermo.rst

@@ -12,10 +12,15 @@ RDKit
 ================
 
 Project home on GitHub: https://github.com/rdkit/rdkit
-Installation instructions: http://code.google.com/p/rdkit/wiki/GettingStarted
 
+Installation instructions: http://code.google.com/p/rdkit/wiki/GettingStarted
 Build it with InChI support.
 
+Mac users with `homebrew <http://brew.sh/>`_ can install it most easily with::
+
+	brew tap edc/homebrew-rdkit
+	brew install rdkit --with-inchi
+
 You'll need various environment variables set, eg.::
 
 	export RDBASE=$HOME/rdkit # CHECK THIS (maybe you put RDKit somewhere else)