[wip/metapod] Document aggressive optimization flags in DESCR.

metapod/DESCR

@@ -4,4 +4,9 @@ templates, such that each algorithm remains model-independant, yet is
 optimized for a particular robot at compile-time.
 
 As of today, the following algorithms have been implemented:
-- RNEA (Recursive Newton Euler Algorithm) for inverse dynamics.
\ No newline at end of file
+- RNEA (Recursive Newton Euler Algorithm) for inverse dynamics.
+
+This software is designed to be a low-level library, performance is
+thus a key issue. For increased performance, it is strongly
+recommended to add the "-march=native -mfpmath=sse" flags to the
+CMAKE_CXX_FLAGS variable before compiling it.
\ No newline at end of file