In README denote that GitHub version should be considered a beta, put link to Amber website.

Author: drroe

README.md

@@ -1,9 +1,16 @@
-About CPPTRAJ
-=============
+CPPTRAJ
+=======
 
 CPPTRAJ is a program designed to load and analyze molecular dynamics
 trajectories and relevant data sets derived from their analysis.
 
+*Note that the GitHub version of CPPTRAJ should be considered BETA.*
+The official AmberTools release version of CPPTRAJ can be found
+at the [Amber website](http://ambermd.org).
+
+About CPPTRAJ
+=============
+
 CPPTRAJ is a rewrite of the PTRAJ trajectory analysis code in C++ that is part
 of AmberTools. The intent is to make the code more readable, leak-free, and
 thread-safe. The biggest functional change from PTRAJ is the ability to load and