Minor command line argument fix in the README

stpm-keygen was documented as taking "-f" for the key filename, when in
fact it uses "-o" for the output filename.
Add C_GetSlotInfo

This allows p11-tool to list all the tokens.
Add enough stubs to pass pkcs11-tool --test

This is done mostly by lying through our teeth about how we don't
support anything.
Merge github.com:isomer/simple-tpm-pk11
Merge pull request #5 from isomer/master

Add enough to pass pkcs11-tool --test