mention "setup.py speed" in README

Author: warner

README.md

@@ -35,7 +35,7 @@ The following table shows how long this library takes to generate keypairs
 (keygen=), to sign data (sign=), and to verify those signatures (verify=), on
 my 2008 Mac laptop. All times are in seconds. It also shows the length of a
 signature (in bytes): the verifying ("public") key is typically the same
-length as the signature, and the signing ("private") key is half that length.
+length as the signature, and the signing ("private") key is half that length. Use "python setup.py speed" to generate this table on your own computer.
 
 * NIST192p: siglen= 48, keygen=0.160s, sign=0.058s, verify=0.116s
 * NIST224p: siglen= 56, keygen=0.230s, sign=0.086s, verify=0.165s