Bumps libpst version to fix TIKA-1350

When parsing some emails in a PST file I get the error "Unknown message type: IPM.Note" preventing them from being parsed. This is because of an extra null byte at the end of the message class string.
This has been fixed in version 0.8.1 of java-libpst so a version bump is all that is required. 
https://github.com/rjohnsondev/java-libpst/issues/14