update doc

Author: zingale

docs/source/ack.rst

@@ -47,5 +47,6 @@ using the Numeric array package and handwritten C extensions for the
 compute-intensive kernels.  It was ported to numarray when that
 replaced Numeric, and continued to use C extensions.  This version
 "pyro2" was resurrected beginning in 2012 and rewritten for numpy
-using f2py, and brought up to date.
+using f2py, and brought up to date.  Most recently we've dropped
+f2py and are using numba for the compute-intensive kernels.