README: point to latest release
README: point to latest release

Update README to point to the just tagged 3.1.4 release

Signed-off-by: Joshua Lock <9750fc34162235efa862f2505c1a01f735e97af7@intel.com>

01org/tpm2.0-tools,martinezjavier/tpm2-tools,martinezjavier/tpm2-tools,01org/tpm2.0-tools,martinezjavier/tpm2-tools,martinezjavier/tpm2-tools,01org/tpm2.0-tools