v0.6.4

More fixes and logging improvements

• Fix a bug where go servers using the portal API to get a CA signed
  cert would fail to connect after 10 days. This was because of a bug
  introduced in v0.6.2 that caused the new CA certs to not be accepted
  for pre-existing registrations that got renewed for a long time.
• The portal client library now re-registers if it gets an error from
  the server when it tries to renew saying the lease isn't registered.
  • This makes it more robust for multiple-machine setups where one
    might stay alive while the other one is restarted or altered or one
    could go into sleep mode etc.
  • I deprecated the KeepLeaseRenewed functions because they don't have
    the ability to re-register since they don't have the registration
    request in the API. StartRegistration is better anyway.
• Now if you use syslog the version information is logged on startup in
  each binary
• Now panics of spawn or any binary launched by spawn are syslogged,
  previously they only showed up on stdout.
• Improved error logging and more info logging for future debugging